diff --git a/src/aws-cpp-sdk-core/include/aws/core/utils/json/JsonSerializer.h b/src/aws-cpp-sdk-core/include/aws/core/utils/json/JsonSerializer.h
index 8b2ccc139bb5..ae98f6c18ff9 100644
--- a/src/aws-cpp-sdk-core/include/aws/core/utils/json/JsonSerializer.h
+++ b/src/aws-cpp-sdk-core/include/aws/core/utils/json/JsonSerializer.h
@@ -94,6 +94,12 @@ namespace Aws
                 JsonValue& WithString(const Aws::String& key, const Aws::String& value);
                 JsonValue& WithString(const char* key, const Aws::String& value);
 
+                /**
+                 * Adds a null value to the top level of this node with key.
+                 */
+                JsonValue& WithNull(const Aws::String& key);
+                JsonValue& WithNull(const char* key);
+
                 /**
                  * Converts the current JSON node to a string.
                  */
diff --git a/src/aws-cpp-sdk-core/source/utils/json/JsonSerializer.cpp b/src/aws-cpp-sdk-core/source/utils/json/JsonSerializer.cpp
index 3cdcac1a8127..bbf44e5b57de 100644
--- a/src/aws-cpp-sdk-core/source/utils/json/JsonSerializer.cpp
+++ b/src/aws-cpp-sdk-core/source/utils/json/JsonSerializer.cpp
@@ -153,6 +153,23 @@ JsonValue& JsonValue::WithString(const Aws::String& key, const Aws::String& valu
     return WithString(key.c_str(), value);
 }
 
+JsonValue& JsonValue::WithNull(const char* key)
+{
+    if (!m_value)
+    {
+        m_value = cJSON_AS4CPP_CreateObject();
+    }
+
+    const auto val = cJSON_AS4CPP_CreateNull();
+    AddOrReplace(m_value, key, val);
+    return *this;
+}
+
+JsonValue& JsonValue::WithNull(const Aws::String& key)
+{
+    return WithNull(key.c_str());
+}
+
 JsonValue& JsonValue::AsString(const Aws::String& value)
 {
     Destroy();
diff --git a/tests/aws-cpp-sdk-core-tests/utils/json/JsonSerializerTest.cpp b/tests/aws-cpp-sdk-core-tests/utils/json/JsonSerializerTest.cpp
index 12234707833f..00f313f9752d 100644
--- a/tests/aws-cpp-sdk-core-tests/utils/json/JsonSerializerTest.cpp
+++ b/tests/aws-cpp-sdk-core-tests/utils/json/JsonSerializerTest.cpp
@@ -434,6 +434,39 @@ TEST_F(JsonSerializerTest, TestGetAllObjects)
     ASSERT_EQ(42, all["Key2"].AsInteger());
 }
 
+TEST_F(JsonSerializerTest, TestWithNull)
+{
+    JsonValue value;
+    value.WithString("Key1", "value1");
+    value.WithNull("Key2");
+    value.WithNull(Aws::String("Key3"));
+    value.WithInteger("Key4", 42);
+
+    auto view = value.View();
+
+    ASSERT_TRUE(view.KeyExists("Key2"));
+    ASSERT_FALSE(view.ValueExists("Key2"));
+    ASSERT_TRUE(view.GetObject("Key2").IsNull());
+
+    ASSERT_TRUE(view.KeyExists("Key3"));
+    ASSERT_FALSE(view.ValueExists("Key3"));
+    ASSERT_TRUE(view.GetObject("Key3").IsNull());
+
+    ASSERT_STREQ("value1", view.GetString("Key1").c_str());
+    ASSERT_EQ(42, view.GetInteger("Key4"));
+
+    Aws::String serialized = view.WriteCompact();
+    JsonValue reparsed(serialized);
+    ASSERT_TRUE(reparsed.WasParseSuccessful());
+    auto reparsedView = reparsed.View();
+    ASSERT_TRUE(reparsedView.KeyExists("Key2"));
+    ASSERT_FALSE(reparsedView.ValueExists("Key2"));
+    ASSERT_TRUE(reparsedView.GetObject("Key2").IsNull());
+    ASSERT_TRUE(reparsedView.KeyExists("Key3"));
+    ASSERT_FALSE(reparsedView.ValueExists("Key3"));
+    ASSERT_TRUE(reparsedView.GetObject("Key3").IsNull());
+}
+
 TEST_F(JsonSerializerTest, TestEquality)
 {
     auto input = R"({"AWS" : {
diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/c2j/C2jShape.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/c2j/C2jShape.java
index fdcde4780145..af13deb827bb 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/c2j/C2jShape.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/c2j/C2jShape.java
@@ -36,4 +36,5 @@ public class C2jShape {
     private boolean sensitive;
     private boolean document;
     private Map<String, Boolean> retryable;
+    private boolean sparse;
 }
diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/Shape.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/Shape.java
index fe953ce7a6b7..478056141298 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/Shape.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/Shape.java
@@ -63,6 +63,7 @@ public class Shape {
     private boolean overrideStreaming = false;
     private boolean requestCompressionRequired=false;
     private boolean requestCompressionRequiredGzip=false;
+    private boolean sparse=false;
 
     public boolean isMap() {
         return "map".equals(type.toLowerCase());
diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/CppShapeInformation.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/CppShapeInformation.java
index 4ca717849337..9e91eac943e0 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/CppShapeInformation.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/CppShapeInformation.java
@@ -31,11 +31,15 @@ public class CppShapeInformation {
    private final String requestContentType;
 
    public CppShapeInformation(final Shape shape, final ServiceModel serviceModel) {
+       this(shape, serviceModel, CppViewHelper.computeCppType(shape));
+   }
+
+   public CppShapeInformation(final Shape shape, final ServiceModel serviceModel, final String cppType) {
        this.shape = shape;
        this.serviceModel = serviceModel;
        className = shape.getName();
        exportValue = CppViewHelper.computeExportValue(serviceModel.getMetadata().getClassNamePrefix());
-       cppType = CppViewHelper.computeCppType(shape);
+       this.cppType = cppType;
        headerIncludes = CppViewHelper.computeHeaderIncludes(serviceModel.getMetadata().getProjectName(), shape);
        sourceIncludes = CppViewHelper.computeSourceIncludes(serviceModel.getMetadata().getProjectName(), shape);
        sourceIncludes.removeAll(headerIncludes);
diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/CppViewHelper.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/CppViewHelper.java
index 9c215a955ca3..46ec36646c32 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/CppViewHelper.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/CppViewHelper.java
@@ -225,12 +225,18 @@ else if(shape.isStructure() || shape.isEnum())
 
         else if(shape.isList()) {
             String type = computeCppTypeInternal(shape.getListMember().getShape(), typeMapping);
+            if (shape.isSparse()) {
+                return String.format("Aws::Vector<Aws::Crt::Optional<%s>>", type);
+            }
             return String.format("Aws::Vector<%s>", type);
         }
 
         else if(shape.isMap()) {
             String key = computeCppTypeInternal(shape.getMapKey().getShape(), typeMapping);
             String value = computeCppTypeInternal(shape.getMapValue().getShape(), typeMapping);
+            if (shape.isSparse()) {
+                return String.format("Aws::Map<%s, Aws::Crt::Optional<%s>>", key, value);
+            }
             return String.format("Aws::Map<%s, %s>", key, value);
         }
 
@@ -387,6 +393,9 @@ public static Set<String> computeHeaderIncludes(String projectName, Shape shape)
                     headers.add(formatModelIncludeName(projectName, shapeInList));
                 }
             }
+            if (next.isSparse()) {
+                headers.add("<aws/crt/Optional.h>");
+            }
             if(!next.isPrimitive()) {
                 if (next.isException() && !next.isModeledException()) {
                     // C++ SDK code generator skips generating exceptions that can be expressed using
diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/CborCppClientGenerator.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/CborCppClientGenerator.java
index 30a999a3c034..8004ca6718bd 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/CborCppClientGenerator.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/CborCppClientGenerator.java
@@ -13,6 +13,7 @@
 import com.amazonaws.util.awsclientgenerator.domainmodels.codegeneration.cpp.CppCborViewHelper;
 import com.amazonaws.util.awsclientgenerator.domainmodels.codegeneration.cpp.CppShapeInformation;
 import com.amazonaws.util.awsclientgenerator.domainmodels.codegeneration.cpp.CppViewHelper;
+import org.apache.commons.lang3.tuple.Pair;
 import org.apache.velocity.Template;
 import org.apache.velocity.VelocityContext;
 
@@ -30,6 +31,18 @@ public CborCppClientGenerator() throws Exception {
         super();
     }
 
+    @Override
+    protected Map<String, CppShapeInformation> buildShapeInformationCache(final ServiceModel serviceModel) {
+        return serviceModel.getShapes().values().stream()
+            .map(shape -> Pair.of(shape.getName(), new CppShapeInformation(shape, serviceModel, CppCborViewHelper.computeCppType(shape))))
+            .collect(Collectors.toMap(Pair::getKey, Pair::getValue));
+    }
+
+    @Override
+    protected Class<?> getViewHelperClass() {
+        return CppCborViewHelper.class;
+    }
+
     @Override
     protected SdkFileEntry generateErrorMarshallerHeaderFile(ServiceModel serviceModel) throws Exception {
         Template template = velocityEngine.getTemplate("/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborErrorMarshallerHeader.vm", StandardCharsets.UTF_8.name());
@@ -78,7 +91,7 @@ protected SdkFileEntry generateModelHeaderFile(ServiceModel serviceModel, Map.En
             }
 
             context.put("shape", shape);
-            context.put("typeInfo", new CppShapeInformation(shape, serviceModel));
+            context.put("typeInfo", new CppShapeInformation(shape, serviceModel, CppCborViewHelper.computeCppType(shape)));
             context.put("CppViewHelper", CppCborViewHelper.class);
 
             String fileName = String.format("include/aws/%s/model/%s.h", serviceModel.getMetadata().getProjectName(),
@@ -149,7 +162,7 @@ else if (shape.isResult()) {
             }
 
             context.put("shape", shape);
-            context.put("typeInfo", new CppShapeInformation(shape, serviceModel));
+            context.put("typeInfo", new CppShapeInformation(shape, serviceModel, CppCborViewHelper.computeCppType(shape)));
             context.put("CppViewHelper", CppCborViewHelper.class);
 
             String fileName = String.format("source/model/%s.cpp", shapeEntry.getKey());
diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/CppClientGenerator.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/CppClientGenerator.java
index edefbb2045a8..4cdf5f7c7968 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/CppClientGenerator.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/CppClientGenerator.java
@@ -88,9 +88,7 @@ public SdkFileEntry[] generateSourceFiles(ServiceModel serviceModel) throws Exce
         addEventStreamInitialResponse(serviceModel);
         addRequestIdToResults(serviceModel);
         List<SdkFileEntry> fileList = new ArrayList<>();
-        final Map<String, CppShapeInformation> shapeInformationCache = serviceModel.getShapes().values().stream()
-            .map(shape -> Pair.of(shape.getName(), new CppShapeInformation(shape, serviceModel)))
-            .collect(Collectors.toMap(Pair::getKey, Pair::getValue));
+        final Map<String, CppShapeInformation> shapeInformationCache = buildShapeInformationCache(serviceModel);
         fileList.addAll(generateModelHeaderFiles(serviceModel, shapeInformationCache));
         fileList.addAll(generateModelSourceFiles(serviceModel, shapeInformationCache));
         fileList.add(generateClientHeaderFile(serviceModel));
@@ -256,6 +254,16 @@ private void CheckAndEnableSigV4A(final ServiceModel serviceModel, VelocityConte
         }
     }
 
+    protected Map<String, CppShapeInformation> buildShapeInformationCache(final ServiceModel serviceModel) {
+        return serviceModel.getShapes().values().stream()
+            .map(shape -> Pair.of(shape.getName(), new CppShapeInformation(shape, serviceModel)))
+            .collect(Collectors.toMap(Pair::getKey, Pair::getValue));
+    }
+
+    protected Class<?> getViewHelperClass() {
+        return CppViewHelper.class;
+    }
+
     protected final VelocityContext createContext(final ServiceModel serviceModel) {
         VelocityContext context = new VelocityContext();
         context.put("nl", System.lineSeparator());
@@ -326,7 +334,7 @@ else if (shape.isEvent() && "blob".equals(shape.getEventPayloadType())) {
         }
         context.put("shape", shape);
         context.put("typeInfo", shapeInformationCache.get(shape.getName()));
-        context.put("CppViewHelper", CppViewHelper.class);
+        context.put("CppViewHelper", getViewHelperClass());
 
         String fileName = String.format("include/aws/%s/model/%s.h", serviceModel.getMetadata().getProjectName(),
                 shapeEntry.getKey());
diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/transform/C2jModelToGeneratorModelTransformer.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/transform/C2jModelToGeneratorModelTransformer.java
index 1838d2c7b59a..89ed4e05ab95 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/transform/C2jModelToGeneratorModelTransformer.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/transform/C2jModelToGeneratorModelTransformer.java
@@ -439,6 +439,10 @@ Shape convertShapeBasics(C2jShape c2jShape, String shapeName) {
         shape.setEvent(c2jShape.isEvent());
         shape.setException(c2jShape.isException());
         shape.setDocument(c2jShape.isDocument());
+        shape.setSparse(c2jShape.isSparse());
+        if (shape.isSparse() && !shape.isList() && !shape.isMap()) {
+            throw new SourceGenerationFailedException("The sparse trait is only applicable to list and map shapes, but was found on shape: " + shape.getName());
+        }
 
         if (c2jShape.getXmlNamespace() != null) {
             XmlNamespace xmlns = new XmlNamespace();
@@ -850,6 +854,7 @@ Shape cloneShape(Shape shape) {
         cloned.setException(shape.isException());
         cloned.setXmlNamespace(shape.getXmlNamespace());
         cloned.setDocument(shape.isDocument());
+        cloned.setSparse(shape.isSparse());
         return cloned;
     }
 
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/ModelClassHeaderMembersSource.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/ModelClassHeaderMembersSource.vm
index ba5ccc5bed0a..de43e1bd99a8 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/ModelClassHeaderMembersSource.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/ModelClassHeaderMembersSource.vm
@@ -42,7 +42,11 @@
   ${spaces}for(const auto& item : $memberVarName)
   ${spaces}{
   ${spaces}  ss << "${locationName}" << item.first;
+#if($member.shape.sparse)
+  ${spaces}  if(item.second.has_value()) { headers.emplace(ss.str(), item.second.value()); }
+#else
   ${spaces}  headers.emplace(ss.str(), item.second);
+#end
   ${spaces}  ss.str("");
   ${spaces}}
 #elseif($member.shape.list)
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/ModelClassMembersAndInlines.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/ModelClassMembersAndInlines.vm
index 19804fce8c45..5af591b469a0 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/ModelClassMembersAndInlines.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/ModelClassMembersAndInlines.vm
@@ -111,6 +111,24 @@
 #set($mapMember = $member.value.shape)
 #set($keyType = $CppViewHelper.computeCppType($mapMember.mapKey.shape))
 #set($valueType = $CppViewHelper.computeCppType($mapMember.mapValue.shape))
+#if($mapMember.sparse)
+#set($optionalValueType = "Aws::Crt::Optional<${valueType}>")
+#if(!$mapMember.mapKey.shape.primitive && !$mapMember.mapKey.shape.enum && !$mapMember.mapValue.shape.primitive && !$mapMember.mapValue.shape.enum)
+#set($keyTemplType = "${memberKeyWithFirstLetterCapitalized}KeyT")
+#set($valueTemplType = "${memberKeyWithFirstLetterCapitalized}ValueT")
+    template<typename ${keyTemplType} = $keyType, typename ${valueTemplType} = $optionalValueType>
+    ${classNameRef} Add${memberKeyWithFirstLetterCapitalized}(${keyTemplType}&& key, ${valueTemplType}&& value) {
+      ${setHasBeenSet}${memberVariableName}.emplace(std::forward<${keyTemplType}>(key), std::forward<${valueTemplType}>(value)); return *this;
+    }
+#else
+    ${inline}${classNameRef} Add${memberKeyWithFirstLetterCapitalized}(${keyType} key, ${valueType} value) {
+      ${setHasBeenSet}${memberVariableName}.emplace(key, value); return *this;
+    }
+#end
+    ${inline}${classNameRef} Add${memberKeyWithFirstLetterCapitalized}(${keyType} key, ${optionalValueType} value) {
+      ${setHasBeenSet}${memberVariableName}.emplace(key, value); return *this;
+    }
+#else
 #if(!$mapMember.mapKey.shape.primitive && !$mapMember.mapKey.shape.enum && !$mapMember.mapValue.shape.primitive && !$mapMember.mapValue.shape.enum)
 #set($keyTemplType = "${memberKeyWithFirstLetterCapitalized}KeyT")
 #set($valueTemplType = "${memberKeyWithFirstLetterCapitalized}ValueT")
@@ -124,9 +142,21 @@
     }
 #end
 #end
+#end
 #if($member.value.shape.list)
 #set($listMember = $member.value.shape)
 #set($valueType = $CppViewHelper.computeCppType($listMember.listMember.shape))
+#if($listMember.sparse)
+#set($optionalValueType = "Aws::Crt::Optional<${valueType}>")
+#if(!$listMember.listMember.shape.primitive && !$listMember.listMember.shape.enum)
+#set($valueTemplType = "${memberKeyWithFirstLetterCapitalized}T")
+    template<typename ${valueTemplType} = $valueType>
+    ${classNameRef} Add${memberKeyWithFirstLetterCapitalized}(${valueTemplType}&& value) { ${setHasBeenSet}${memberVariableName}.emplace_back(std::forward<${valueTemplType}>(value)); return *this; }
+#else
+    ${inline}${classNameRef} Add${memberKeyWithFirstLetterCapitalized}(${valueType} value)$adderWithCopy
+#end
+    ${inline}${classNameRef} Add${memberKeyWithFirstLetterCapitalized}(${optionalValueType} value)$adderWithCopy
+#else
 #if(!$listMember.listMember.shape.primitive && !$listMember.listMember.shape.enum)
 #set($valueTemplType = "${memberKeyWithFirstLetterCapitalized}T")
     template<typename ${valueTemplType} = $valueType>
@@ -134,6 +164,7 @@
 #else
     ${inline}${classNameRef} Add${memberKeyWithFirstLetterCapitalized}(${valueType} value)$adderWithCopy
 #end
+#end
 #end
     ///@}
 #end##if(!($CppViewHelper.isStreamingPayloadMember($shape, $member.key) && $shape.request))
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborDecodeListValue.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborDecodeListValue.vm
index 9a47a159e28b..6474947eaa89 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborDecodeListValue.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborDecodeListValue.vm
@@ -1,7 +1,24 @@
+#set($parentListDepth = $recursionDepth - 1)
+#if($member.shape.sparse)
+{
+    auto nullPeek_${recursionDepth} = decoder->PeekType();
+    if (nullPeek_${recursionDepth}.has_value() && nullPeek_${recursionDepth}.value() == Aws::Crt::Cbor::CborType::Null) {
+        decoder->ConsumeNextSingleElement();
+#if($parentListDepth == 0)
+        ${memberVarName}.emplace_back();
+#else
+        nestedList_${parentListDepth}.emplace_back();
+#end
+    } else {
+#end
 #if($shapeMember.enum)
 auto ${containerVar} = decoder->PopNextTextVal();
 if (${containerVar}.has_value()) {
-    ${value}.push_back(${shapeMember.name}Mapper::Get${shapeMember.name}ForName(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len)));
+#if($parentListDepth == 0)
+    ${memberVarName}.push_back(${shapeMember.name}Mapper::Get${shapeMember.name}ForName(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len)));
+#else
+    nestedList_${parentListDepth}.push_back(${shapeMember.name}Mapper::Get${shapeMember.name}ForName(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len)));
+#end
     }
 #elseif($shapeMember.string)
 auto peekType_${recursionDepth} = decoder->PeekType();
@@ -9,7 +26,11 @@ if(peekType_${recursionDepth}.has_value()){
     if (peekType_${recursionDepth}.value() == Aws::Crt::Cbor::CborType::Text) {
         auto ${containerVar} = decoder->PopNextTextVal();
         if (${containerVar}.has_value()) {
-            ${value}.push_back(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len));
+#if($parentListDepth == 0)
+            ${memberVarName}.push_back(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len));
+#else
+            nestedList_${parentListDepth}.push_back(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len));
+#end
         }
     } else {
         decoder->ConsumeNextSingleElement();
@@ -27,24 +48,40 @@ if(peekType_${recursionDepth}.has_value()){
                 ss_${recursionDepth} << Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len);
             }
         }
-        ${value}.push_back(ss_${recursionDepth}.str());
+#if($parentListDepth == 0)
+        ${memberVarName}.push_back(ss_${recursionDepth}.str());
+#else
+        nestedList_${parentListDepth}.push_back(ss_${recursionDepth}.str());
+#end
         ss_${recursionDepth}.clear();
     }
 }
 #elseif($shapeMember.boolean)
     auto ${containerVar} = decoder->PopNextBooleanVal();
     if (${containerVar}.has_value()) {
-    ${value}.push_back(${containerVar}.value());
+#if($parentListDepth == 0)
+    ${memberVarName}.push_back(${containerVar}.value());
+#else
+    nestedList_${parentListDepth}.push_back(${containerVar}.value());
+#end
     }
 #elseif($shapeMember.double)
     auto ${containerVar} = decoder->PopNextFloatVal();
     if (${containerVar}.has_value()) {
-    ${value}.push_back(${containerVar}.value());
+#if($parentListDepth == 0)
+    ${memberVarName}.push_back(${containerVar}.value());
+#else
+    nestedList_${parentListDepth}.push_back(${containerVar}.value());
+#end
     }
 #elseif($shapeMember.float)
     auto ${containerVar} = decoder->PopNextFloatVal();
     if (${containerVar}.has_value()) {
-    ${value}.push_back(${containerVar}.value());
+#if($parentListDepth == 0)
+    ${memberVarName}.push_back(${containerVar}.value());
+#else
+    nestedList_${parentListDepth}.push_back(${containerVar}.value());
+#end
     }
 #elseif($shapeMember.blob)
     auto peekType_${recursionDepth} = decoder->PeekType();
@@ -52,7 +89,11 @@ if(peekType_${recursionDepth}.has_value()){
         if (peekType_${recursionDepth}.value() == Aws::Crt::Cbor::CborType::Bytes) {
             auto ${containerVar} = decoder->PopNextBytesVal();
             if (${containerVar}.has_value()) {
-                ${value}.push_back(Aws::Utils::ByteBuffer(${containerVar}.value().ptr, ${containerVar}.value().len));
+#if($parentListDepth == 0)
+                ${memberVarName}.push_back(Aws::Utils::ByteBuffer(${containerVar}.value().ptr, ${containerVar}.value().len));
+#else
+                nestedList_${parentListDepth}.push_back(Aws::Utils::ByteBuffer(${containerVar}.value().ptr, ${containerVar}.value().len));
+#end
             }
         } else {
             decoder->ConsumeNextSingleElement();
@@ -70,7 +111,11 @@ if(peekType_${recursionDepth}.has_value()){
                     ss_${recursionDepth} << Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len);
                 }
             }
-            ${value}.push_back(Aws::Utils::ByteBuffer(ss_${recursionDepth}.str()));
+#if($parentListDepth == 0)
+            ${memberVarName}.push_back(Aws::Utils::ByteBuffer(ss_${recursionDepth}.str()));
+#else
+            nestedList_${parentListDepth}.push_back(Aws::Utils::ByteBuffer(ss_${recursionDepth}.str()));
+#end
             ss_${recursionDepth}.clear();
         }
     }
@@ -85,23 +130,39 @@ if(peekType_${recursionDepth}.has_value()){
             {
                 auto ${containerVar} = decoder->PopNextFloatVal();
                 if (${containerVar}.has_value()) {
-                    ${value}.push_back(Aws::Utils::DateTime(${containerVar}.value()));
+#if($parentListDepth == 0)
+                    ${memberVarName}.push_back(Aws::Utils::DateTime(${containerVar}.value()));
+#else
+                    nestedList_${parentListDepth}.push_back(Aws::Utils::DateTime(${containerVar}.value()));
+#end
                 }
             }
             else
             {
                 auto ${containerVar} = decoder->PopNextUnsignedIntVal();
                 if (${containerVar}.has_value()) {
-                    ${value}.push_back(Aws::Utils::DateTime(${containerVar}.value()));
+#if($parentListDepth == 0)
+                    ${memberVarName}.push_back(Aws::Utils::DateTime(${containerVar}.value()));
+#else
+                    nestedList_${parentListDepth}.push_back(Aws::Utils::DateTime(${containerVar}.value()));
+#end
                 }
             }
         }
     }
 #elseif($shapeMember.structure)
     #if($member.shape.isMutuallyReferencedWith($shape) || $member.shape.getName() == $shape.getName())
-        ${value}.push_back(Aws::MakeShared<${shapeMember.name}>("${typeInfo.className}", ${shapeMember.name}(decoder)));
+#if($parentListDepth == 0)
+        ${memberVarName}.push_back(Aws::MakeShared<${shapeMember.name}>("${typeInfo.className}", ${shapeMember.name}(decoder)));
+#else
+        nestedList_${parentListDepth}.push_back(Aws::MakeShared<${shapeMember.name}>("${typeInfo.className}", ${shapeMember.name}(decoder)));
+#end
     #else
-        ${value}.push_back(${shapeMember.name}(decoder));
+#if($parentListDepth == 0)
+        ${memberVarName}.push_back(${shapeMember.name}(decoder));
+#else
+        nestedList_${parentListDepth}.push_back(${shapeMember.name}(decoder));
+#end
     #end
 #elseif($shapeMember.list)
     #set($template.nestedShapeMember = $shapeMember.listMember.shape)
@@ -145,7 +206,7 @@ if(peekType_${recursionDepth}.has_value()){
       }
       #if($recursionDepth > 1)
         #set($parentDepth = $recursionDepth - 1)
-        nestedList_${parentDepth}.push_back(${value});
+        nestedList_${parentDepth}.push_back(nestedList_${recursionDepth});
       #else
       ${memberVarName}.push_back(nestedList_${recursionDepth});
       #end
@@ -191,7 +252,7 @@ if(peekType_${recursionDepth}.has_value()){
       }
       #if($recursionDepth > 1)
         #set($parentDepth = $recursionDepth - 1)
-        nestedList_${parentDepth}.push_back(${value});
+        nestedList_${parentDepth}.push_back(nestedMap_${recursionDepth});
       #else
       ${memberVarName}.push_back(nestedMap_${recursionDepth});
       #end
@@ -202,13 +263,25 @@ if(peekType_${recursionDepth}.has_value()){
     if(peekType_${recursionDepth}.value() == Aws::Crt::Cbor::CborType::UInt){
         auto ${containerVar} = decoder->PopNextUnsignedIntVal();
         if (${containerVar}.has_value()) {
-            ${value}.push_back(static_cast<int64_t>(${containerVar}.value()));
+#if($parentListDepth == 0)
+            ${memberVarName}.push_back(static_cast<int64_t>(${containerVar}.value()));
+#else
+            nestedList_${parentListDepth}.push_back(static_cast<int64_t>(${containerVar}.value()));
+#end
         }
     } else {
         auto ${containerVar} = decoder->PopNextNegativeIntVal();
         if (${containerVar}.has_value()) {
-            ${value}.push_back(static_cast<int64_t>(1 - ${containerVar}.value()));
+#if($parentListDepth == 0)
+            ${memberVarName}.push_back(static_cast<int64_t>(1 - ${containerVar}.value()));
+#else
+            nestedList_${parentListDepth}.push_back(static_cast<int64_t>(1 - ${containerVar}.value()));
+#end
         }
     }
 }
-#end
\ No newline at end of file
+#end
+#if($member.shape.sparse)
+    } // end else (non-null sparse element)
+}
+#end
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborDecodeMapValue.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborDecodeMapValue.vm
index 29bd1683e133..c48255d584c0 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborDecodeMapValue.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborDecodeMapValue.vm
@@ -1,10 +1,27 @@
+#set($parentMapDepth = $recursionDepth - 1)
 auto key_${recursionDepth} = decoder->PopNextTextVal();
 if (key_${recursionDepth}.has_value()) {
     Aws::String keyStr_${recursionDepth} = Aws::String(reinterpret_cast<const char*>(key_${recursionDepth}.value().ptr), key_${recursionDepth}.value().len);
+#if($member.shape.sparse)
+    {
+    auto nullPeek_${recursionDepth} = decoder->PeekType();
+    if (nullPeek_${recursionDepth}.has_value() && nullPeek_${recursionDepth}.value() == Aws::Crt::Cbor::CborType::Null) {
+        decoder->ConsumeNextSingleElement();
+#if($parentMapDepth == 0)
+        ${memberVarName}[keyStr_${recursionDepth}];
+#else
+        nestedMap_${parentMapDepth}[keyStr_${recursionDepth}];
+#end
+    } else {
+#end
 #if($shapeMember.enum)
     auto ${containerVar} = decoder->PopNextTextVal();
     if (${containerVar}.has_value()) {
-        ${value}[keyStr_${recursionDepth}] = ${shapeMember.name}Mapper::Get${shapeMember.name}ForName(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len));
+#if($parentMapDepth == 0)
+        ${memberVarName}[keyStr_${recursionDepth}] = ${shapeMember.name}Mapper::Get${shapeMember.name}ForName(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len));
+#else
+        nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = ${shapeMember.name}Mapper::Get${shapeMember.name}ForName(Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len));
+#end
     }
 #elseif($shapeMember.string)
 auto peekType_${recursionDepth} = decoder->PeekType();
@@ -12,7 +29,11 @@ if(peekType_${recursionDepth}){
     if (peekType_${recursionDepth}.value() == Aws::Crt::Cbor::CborType::Text) {
         auto ${containerVar} = decoder->PopNextTextVal();
         if (${containerVar}.has_value()) {
-            ${value}[keyStr_${recursionDepth}] = Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len);
+#if($parentMapDepth == 0)
+            ${memberVarName}[keyStr_${recursionDepth}] = Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len);
+#else
+            nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len);
+#end
         }
     } else {
         decoder->ConsumeNextSingleElement();
@@ -30,24 +51,40 @@ if(peekType_${recursionDepth}){
                 ss_${recursionDepth} << Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len);
             }
         }
-            ${value}[keyStr_${recursionDepth}] = ss_${recursionDepth}.str();
+#if($parentMapDepth == 0)
+            ${memberVarName}[keyStr_${recursionDepth}] = ss_${recursionDepth}.str();
+#else
+            nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = ss_${recursionDepth}.str();
+#end
             ss_${recursionDepth}.clear();
     }
 }
 #elseif($shapeMember.boolean)
     auto ${containerVar} = decoder->PopNextBooleanVal();
     if (${containerVar}.has_value()) {
-        ${value}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#if($parentMapDepth == 0)
+        ${memberVarName}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#else
+        nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#end
     }
 #elseif($shapeMember.double)
     auto ${containerVar} = decoder->PopNextFloatVal();
     if (${containerVar}.has_value()) {
-        ${value}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#if($parentMapDepth == 0)
+        ${memberVarName}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#else
+        nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#end
     }
 #elseif($shapeMember.float)
     auto ${containerVar} = decoder->PopNextFloatVal();
     if (${containerVar}.has_value()) {
-        ${value}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#if($parentMapDepth == 0)
+        ${memberVarName}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#else
+        nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = ${containerVar}.value();
+#end
     }
 #elseif($shapeMember.blob)
     auto peekType_${recursionDepth} = decoder->PeekType();
@@ -55,7 +92,11 @@ if(peekType_${recursionDepth}){
         if (peekType_${recursionDepth}.value() == Aws::Crt::Cbor::CborType::Bytes) {
             auto ${containerVar} = decoder->PopNextBytesVal();
             if (${containerVar}.has_value()) {
-                ${value}[keyStr_${recursionDepth}] = Aws::Utils::ByteBuffer(${containerVar}.value().ptr, ${containerVar}.value().len);
+#if($parentMapDepth == 0)
+                ${memberVarName}[keyStr_${recursionDepth}] = Aws::Utils::ByteBuffer(${containerVar}.value().ptr, ${containerVar}.value().len);
+#else
+                nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = Aws::Utils::ByteBuffer(${containerVar}.value().ptr, ${containerVar}.value().len);
+#end
             }
         } else {
             decoder->ConsumeNextSingleElement();
@@ -73,7 +114,11 @@ if(peekType_${recursionDepth}){
                     ss_${recursionDepth} << Aws::String(reinterpret_cast<const char*>(${containerVar}.value().ptr), ${containerVar}.value().len);
                 }
             }
-            ${value}[keyStr_${recursionDepth}] = Aws::Utils::ByteBuffer(ss_${recursionDepth}.str());
+#if($parentMapDepth == 0)
+            ${memberVarName}[keyStr_${recursionDepth}] = Aws::Utils::ByteBuffer(ss_${recursionDepth}.str());
+#else
+            nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = Aws::Utils::ByteBuffer(ss_${recursionDepth}.str());
+#end
             ss_${recursionDepth}.clear();
         }
     }
@@ -88,23 +133,39 @@ if(peekType_${recursionDepth}){
             {
                 auto ${containerVar} = decoder->PopNextFloatVal();
                 if (${containerVar}.has_value()) {
-                    ${value}[keyStr_${recursionDepth}] = Aws::Utils::DateTime(${containerVar}.value());
+#if($parentMapDepth == 0)
+                    ${memberVarName}[keyStr_${recursionDepth}] = Aws::Utils::DateTime(${containerVar}.value());
+#else
+                    nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = Aws::Utils::DateTime(${containerVar}.value());
+#end
                 }
             }
             else
             {
                 auto ${containerVar} = decoder->PopNextUnsignedIntVal();
                 if (${containerVar}.has_value()) {
-                    ${value}[keyStr_${recursionDepth}] = Aws::Utils::DateTime(${containerVar}.value());
+#if($parentMapDepth == 0)
+                    ${memberVarName}[keyStr_${recursionDepth}] = Aws::Utils::DateTime(${containerVar}.value());
+#else
+                    nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = Aws::Utils::DateTime(${containerVar}.value());
+#end
                 }
             }
         }
     }
 #elseif($shapeMember.structure)
     #if($member.shape.isMutuallyReferencedWith($shape) || $member.shape.getName() == $shape.getName())
-        ${value}[keyStr_${recursionDepth}] = Aws::MakeShared<${shapeMember.name}>("${typeInfo.className}", ${shapeMember.name}(decoder));
+#if($parentMapDepth == 0)
+        ${memberVarName}[keyStr_${recursionDepth}] = Aws::MakeShared<${shapeMember.name}>("${typeInfo.className}", ${shapeMember.name}(decoder));
+#else
+        nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = Aws::MakeShared<${shapeMember.name}>("${typeInfo.className}", ${shapeMember.name}(decoder));
+#end
     #else
-        ${value}[keyStr_${recursionDepth}] = ${shapeMember.name}(decoder);
+#if($parentMapDepth == 0)
+        ${memberVarName}[keyStr_${recursionDepth}] = ${shapeMember.name}(decoder);
+#else
+        nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = ${shapeMember.name}(decoder);
+#end
     #end
 #elseif($shapeMember.map)
     #set($template.nestedShapeMember = $shapeMember.mapValue.shape)
@@ -144,9 +205,9 @@ if(peekType_${recursionDepth}){
           #set($recursionDepth = $recursionDepth - 1)
         }
       }
-      #if($recursionDepth > 0)
+      #if($recursionDepth > 1)
         #set($parentDepth = $recursionDepth - 1)
-        nestedMap_${parentDepth}[keyStr_${recursionDepth}] = ${value};
+        nestedMap_${parentDepth}[keyStr_${recursionDepth}] = nestedMap_${recursionDepth};
       #else
       ${memberVarName}[keyStr_${recursionDepth}] = nestedMap_${recursionDepth};
       #end
@@ -193,7 +254,7 @@ if(peekType_${recursionDepth}){
       }
       #if($recursionDepth > 1)
         #set($parentDepth = $recursionDepth - 1)
-        nestedMap_${parentDepth}[keyStr_${recursionDepth}] = ${value};
+        nestedMap_${parentDepth}[keyStr_${recursionDepth}] = nestedList_${recursionDepth};
       #else
       ${memberVarName}[keyStr_${recursionDepth}] = nestedList_${recursionDepth};
       #end
@@ -204,14 +265,26 @@ if(peekType_${recursionDepth}){
     if(peekType_${recursionDepth}.value() == Aws::Crt::Cbor::CborType::UInt){
         auto ${containerVar} = decoder->PopNextUnsignedIntVal();
         if (${containerVar}.has_value()) {
-            ${value}[keyStr_${recursionDepth}] = static_cast<int64_t>(${containerVar}.value());
+#if($parentMapDepth == 0)
+            ${memberVarName}[keyStr_${recursionDepth}] = static_cast<int64_t>(${containerVar}.value());
+#else
+            nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = static_cast<int64_t>(${containerVar}.value());
+#end
         }
     } else {
         auto ${containerVar} = decoder->PopNextNegativeIntVal();
         if (${containerVar}.has_value()) {
-            ${value}[keyStr_${recursionDepth}] = static_cast<int64_t>(1 - ${containerVar}.value());
+#if($parentMapDepth == 0)
+            ${memberVarName}[keyStr_${recursionDepth}] = static_cast<int64_t>(1 - ${containerVar}.value());
+#else
+            nestedMap_${parentMapDepth}[keyStr_${recursionDepth}] = static_cast<int64_t>(1 - ${containerVar}.value());
+#end
         }
     }
 }
 #end
-}
\ No newline at end of file
+#if($member.shape.sparse)
+    } // end else (non-null sparse value)
+    }
+#end
+}
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborEncodeValue.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborEncodeValue.vm
index 279d4d3dc78f..fd089e19d3d1 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborEncodeValue.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborEncodeValue.vm
@@ -3,21 +3,43 @@ encoder.WriteText(Aws::Crt::ByteCursorFromCString(${shapeMember.name}Mapper::Get
 #elseif($shapeMember.list)
 encoder.WriteArrayStart(${value}.size());
 for(const auto& item_${recursionDepth} : ${value}) {
+#if($shapeMember.sparse)
+    if (!item_${recursionDepth}.has_value()) { encoder.WriteNull(); } else {
+    const auto& sparseItem_${recursionDepth} = *item_${recursionDepth};
+#set($value = "sparseItem_${recursionDepth}")
 #set($shapeMember = $shapeMember.listMember.shape)
+#set($recursionDepth = $recursionDepth + 1)
+#parse("com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborEncodeValue.vm")
+#set($recursionDepth = $recursionDepth - 1)
+    }
+#else
 #set($value = "item_${recursionDepth}")
+#set($shapeMember = $shapeMember.listMember.shape)
 #set($recursionDepth = $recursionDepth + 1)
 #parse("com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborEncodeValue.vm")
 #set($recursionDepth = $recursionDepth - 1)
+#end
 }
 #elseif($shapeMember.map)
 encoder.WriteMapStart(${value}.size());
 for(const auto& item_${recursionDepth} : ${value}) {
     encoder.WriteText(Aws::Crt::ByteCursorFromCString(item_${recursionDepth}.first.c_str()));
+#if($shapeMember.sparse)
+    if (!item_${recursionDepth}.second.has_value()) { encoder.WriteNull(); } else {
+    const auto& sparseVal_${recursionDepth} = *item_${recursionDepth}.second;
+#set($value = "sparseVal_${recursionDepth}")
 #set($shapeMember = $shapeMember.mapValue.shape)
+#set($recursionDepth = $recursionDepth + 1)
+#parse("com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborEncodeValue.vm")
+#set($recursionDepth = $recursionDepth - 1)
+    }
+#else
 #set($value = "item_${recursionDepth}.second")
+#set($shapeMember = $shapeMember.mapValue.shape)
 #set($recursionDepth = $recursionDepth + 1)
 #parse("com/amazonaws/util/awsclientgenerator/velocity/cpp/cbor/CborEncodeValue.vm")
 #set($recursionDepth = $recursionDepth - 1)
+#end
 }
 #elseif($shapeMember.blob)
 encoder.WriteBytes(Aws::Crt::ByteCursorFromCString(reinterpret_cast<const char*>(${value}.GetUnderlyingData())));
@@ -40,4 +62,4 @@ encoder.WriteTag(1); //1 represents Epoch-based date/time. See https://www.rfc-e
 encoder.WriteUInt(${value}.Seconds());
 #else
 (${value} >= 0) ? encoder.WriteUInt(${value}) : encoder.WriteNegInt(${value});
-#end
\ No newline at end of file
+#end
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/json/ModelInternalMapOrListJsonDeserializer.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/json/ModelInternalMapOrListJsonDeserializer.vm
index 492de94d73bc..65d7afff006a 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/json/ModelInternalMapOrListJsonDeserializer.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/json/ModelInternalMapOrListJsonDeserializer.vm
@@ -22,6 +22,13 @@
 #end
   ${template.currentSpaces}for(auto& ${template.lowerCaseVarName}Item : ${template.lowerCaseVarName}JsonMap)
   ${template.currentSpaces}{
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  if(${template.lowerCaseVarName}Item.second.IsNull())
+  ${template.currentSpaces}  {
+  ${template.currentSpaces}    ${template.containerVar}[${template.lowerCaseVarName}Item.first];
+  ${template.currentSpaces}    continue;
+  ${template.currentSpaces}  }
+#end
 #if(!$template.currentShape.mapValue.shape.map && !$template.currentShape.mapValue.shape.list)
 #set($lvalue = "${template.containerVar}[${template.lowerCaseVarName}Item.first]")
 #set($rvalue = "${template.lowerCaseVarName}Item.second.As${CppViewHelper.computeJsonCppType($template.currentShape.mapValue.shape)}()")
@@ -82,18 +89,41 @@
 #end
   ${template.currentSpaces}for(unsigned ${template.lowerCaseVarName}Index = 0; ${template.lowerCaseVarName}Index < ${template.lowerCaseVarName}JsonList.GetLength(); ++${template.lowerCaseVarName}Index)
   ${template.currentSpaces}{
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  if(${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].IsNull())
+  ${template.currentSpaces}  {
+  ${template.currentSpaces}    ${template.containerVar}.emplace_back();
+  ${template.currentSpaces}    continue;
+  ${template.currentSpaces}  }
+#end
 #if(!$template.currentShape.listMember.shape.map && !$template.currentShape.listMember.shape.list)
 #set($template.atBottom = true)
 #if($template.currentShape.listMember.shape.enum)
 #set($enumName = $template.currentShape.listMember.shape.name)
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  ${template.containerVar}.emplace_back(${enumName}Mapper::Get${enumName}ForName(${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].AsString()));
+#else
   ${template.currentSpaces}  ${template.containerVar}.push_back(${enumName}Mapper::Get${enumName}ForName(${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].AsString()));
+#end
 #elseif($template.currentShape.listMember.shape.blob)
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  ${template.containerVar}.emplace_back(HashingUtils::Base64Decode(${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}()));
+#else
   ${template.currentSpaces}  ${template.containerVar}.push_back(HashingUtils::Base64Decode(${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}()));
+#end
 #elseif($template.currentShape.listMember.shape.timeStamp && $template.currentShape.listMember.shape.timestampFormat == "iso8601")
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  ${template.containerVar}.emplace_back(Aws::Utils::DateTime{${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}(), Aws::Utils::DateFormat::$CppViewHelper.computeTimestampFormatInQueryString($template.currentShape.listMember.shape)});
+#else
   ${template.currentSpaces}  ${template.containerVar}.push_back(Aws::Utils::DateTime{${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}(), Aws::Utils::DateFormat::$CppViewHelper.computeTimestampFormatInQueryString($template.currentShape.listMember.shape)});
+#end
+#else
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  ${template.containerVar}.emplace_back(${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}());
 #else
   ${template.currentSpaces}  ${template.containerVar}.push_back(${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}());
 #end
+#end
 #else
 #set($currentSpaces = $template.currentSpaces + "  ")
 #set($currentShape = $template.currentShape.listMember.shape)
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/json/ModelInternalMapOrListJsonize.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/json/ModelInternalMapOrListJsonize.vm
index 56c69280c330..6b102baaae5f 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/json/ModelInternalMapOrListJsonize.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/json/ModelInternalMapOrListJsonize.vm
@@ -13,8 +13,31 @@
   ${template.currentSpaces}JsonValue ${template.lowerCaseVarName}JsonMap;
   ${template.currentSpaces}for(auto& ${template.lowerCaseVarName}Item : ${template.containerVar})
   ${template.currentSpaces}{
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  if(!${template.lowerCaseVarName}Item.second.has_value())
+  ${template.currentSpaces}  {
+  ${template.currentSpaces}    ${template.lowerCaseVarName}JsonMap.WithNull(${template.lowerCaseVarName}Item.first);
+  ${template.currentSpaces}    continue;
+  ${template.currentSpaces}  }
+#end
 #if(!$template.currentShape.mapValue.shape.map && !$template.currentShape.mapValue.shape.list)
 #set($functionCall = "${template.lowerCaseVarName}JsonMap.With${CppViewHelper.computeJsonCppType($template.currentShape.mapValue.shape)}")
+#if($template.currentShape.sparse)
+#set($key = "${template.lowerCaseVarName}Item.first")
+#set($value = "*${template.lowerCaseVarName}Item.second${CppViewHelper.computeJsonizeString($template.currentShape.mapValue.shape)}")
+#if($template.currentShape.mapValue.shape.isBlob())
+#set($value = "HashingUtils::Base64Encode(*${template.lowerCaseVarName}Item.second${CppViewHelper.computeJsonizeString($template.currentShape.mapValue.shape)})")
+#end
+#if($template.currentShape.mapKey.shape.enum)
+#set($enumName = $template.currentShape.mapKey.shape.name)
+#set($key = "${enumName}Mapper::GetNameFor${enumName}(${template.lowerCaseVarName}Item.first)")
+#end
+#if($template.currentShape.mapValue.shape.enum)
+#set($enumName = $template.currentShape.mapValue.shape.name)
+#set($value = "${enumName}Mapper::GetNameFor${enumName}(*${template.lowerCaseVarName}Item.second)")
+#set($functionCall = "${template.lowerCaseVarName}JsonMap.WithString")
+#end
+#else
 #set($key = "${template.lowerCaseVarName}Item.first")
 #set($value = "${template.lowerCaseVarName}Item.second${CppViewHelper.computeJsonizeString($template.currentShape.mapValue.shape)}")
 #if($template.currentShape.mapValue.shape.isBlob())
@@ -28,6 +51,7 @@
 #set($enumName = $template.currentShape.mapValue.shape.name)
 #set($value = "${enumName}Mapper::GetNameFor${enumName}(${value})")
 #set($functionCall = "${template.lowerCaseVarName}JsonMap.WithString")
+#end
 #end
   ${template.currentSpaces}  ${functionCall}(${key}, ${value});
 #set($template.atBottom = true)
@@ -59,16 +83,35 @@
   ${template.currentSpaces}${AwsArray}<JsonValue> ${template.lowerCaseVarName}JsonList(${template.containerVar}.size());
   ${template.currentSpaces}for(unsigned ${template.lowerCaseVarName}Index = 0; ${template.lowerCaseVarName}Index < ${template.lowerCaseVarName}JsonList.GetLength(); ++${template.lowerCaseVarName}Index)
   ${template.currentSpaces}{
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  if(!${template.containerVar}[${template.lowerCaseVarName}Index].has_value())
+  ${template.currentSpaces}  {
+  ${template.currentSpaces}    ${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].AsNull();
+  ${template.currentSpaces}    continue;
+  ${template.currentSpaces}  }
+#end
 #if(!$template.currentShape.listMember.shape.map && !$template.currentShape.listMember.shape.list)
 #set($template.atBottom = true)
 #if($template.currentShape.listMember.shape.enum)
 #set($enumName = $template.currentShape.listMember.shape.name)
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  ${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].AsString(${enumName}Mapper::GetNameFor${enumName}(*${template.containerVar}[${template.lowerCaseVarName}Index]));
+#else
   ${template.currentSpaces}  ${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].AsString(${enumName}Mapper::GetNameFor${enumName}(${template.containerVar}[${template.lowerCaseVarName}Index]));
+#end
 #elseif($template.currentShape.listMember.shape.blob)
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  ${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}(HashingUtils::Base64Encode(*${template.containerVar}[${template.lowerCaseVarName}Index]${CppViewHelper.computeJsonizeString($template.currentShape.listMember.shape)}));
+#else
   ${template.currentSpaces}  ${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}(HashingUtils::Base64Encode(${template.containerVar}[${template.lowerCaseVarName}Index]${CppViewHelper.computeJsonizeString($template.currentShape.listMember.shape)}));
+#end
+#else
+#if($template.currentShape.sparse)
+  ${template.currentSpaces}  ${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}(*${template.containerVar}[${template.lowerCaseVarName}Index]${CppViewHelper.computeJsonizeString($template.currentShape.listMember.shape)});
 #else
   ${template.currentSpaces}  ${template.lowerCaseVarName}JsonList[${template.lowerCaseVarName}Index].As${CppViewHelper.computeJsonCppType($template.currentShape.listMember.shape)}(${template.containerVar}[${template.lowerCaseVarName}Index]${CppViewHelper.computeJsonizeString($template.currentShape.listMember.shape)});
 #end
+#end
 #else
 #set($currentSpaces = $template.currentSpaces + "  ")
 #set($currentShape = $template.currentShape.listMember.shape)
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/request/SetListMacro.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/request/SetListMacro.vm
index 98ee03ac1321..694e9e37e9c2 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/request/SetListMacro.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/request/SetListMacro.vm
@@ -31,6 +31,16 @@ ${macro.spaces}{
 ${macro.spaces}}
 #end##foreach
 #else## not (list || map || structure)
+#if($listShape.sparse)
+#set($macro.fieldAdder = "Add${CppViewHelper.capitalizeFirstChar($testInputParam.key)}")
+#foreach($arrayItem in $testInputParam.value)
+#if($arrayItem == "null")
+${macro.spaces}${dstObject}.${macro.fieldAdder}(Aws::Crt::Optional<$CppViewHelper.computeCppType($macro.listMemberShape)>{});
+#else
+${macro.spaces}${dstObject}.${macro.fieldAdder}(#SerializeSingleParameterMacro($macro.listMemberShape, $arrayItem));
+#end
+#end
+#else
 #set($macro.fieldSetter = "Set${CppViewHelper.capitalizeFirstChar($testInputParam.key)}")
 #set($macro.listResult="{")
 #foreach($arrayItem in $testInputParam.value)
@@ -39,5 +49,6 @@ ${macro.spaces}}
 #end
 #set($macro.listResult=$macro.listResult + "}")
 ${spaces}${dstObject}.${macro.fieldSetter}($macro.listResult);
+#end
 #end##(list || map || structure)
 #end##macro SetListMacro
\ No newline at end of file
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/request/SetMapMacro.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/request/SetMapMacro.vm
index 809e27ce2377..bb2656a29b72 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/request/SetMapMacro.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/request/SetMapMacro.vm
@@ -29,6 +29,16 @@ ${macro.spaces}}
 #break
 #end
 ###----- the map value is not nested structure or document
+#if($mapShape.sparse)
+#set($macro.fieldAdder = "Add${CppViewHelper.capitalizeFirstChar($testInputParam.key)}")
+#foreach($mapItem in $testInputParam.value.fields())
+#if($mapItem.value == "null")
+${macro.spaces}${dstObject}.${macro.fieldAdder}("$mapItem.key", Aws::Crt::Optional<$CppViewHelper.computeCppType($mapShape.mapValue.shape)>{});
+#else
+${macro.spaces}${dstObject}.${macro.fieldAdder}("$mapItem.key", #SerializeSingleParameterMacro($mapShape.mapValue.shape, $mapItem.value));
+#end
+#end
+#else
 #set($macro.mapResult="{")
 #foreach($mapItem in $testInputParam.value.fields())
 #set($macro.mapItem="{" + '"' + "$mapItem.key" + '"' + ",  ")
@@ -38,4 +48,5 @@ ${macro.spaces}}
 #end
 #set($macro.mapResult=$macro.mapResult + "}")
 ${spaces}${dstObject}.${macro.fieldSetter}($macro.mapResult);
+#end
 #end##macro SetMapMacro
\ No newline at end of file
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateListMacro.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateListMacro.vm
index 7c9070a317bd..1dec4b2ea133 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateListMacro.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateListMacro.vm
@@ -23,6 +23,23 @@
 #set($macro.listItemVarName = "${dstObject}${CppViewHelper.capitalizeFirstChar(${CppViewHelper.computeVariableName($testValidateParam.key)})}Item")
 #end
 #if($macro.listMemberShape.list || $macro.listMemberShape.map || $macro.listMemberShape.structure)
+#if($listShape.sparse && $macro.listMemberShape.structure)
+${macro.spaces}const Aws::Vector<Aws::Crt::Optional<$CppViewHelper.computeCppType($macro.listMemberShape)>>& $macro.listItemVarName = ${dstObject}.${macro.fieldGetter};
+${macro.spaces}EXPECT_EQ(${testValidateParamVal.size()}U, ${macro.listItemVarName}.size());
+#foreach($arrayItem in $testValidateParamVal)
+${macro.spaces}{
+#if($arrayItem.isNull())
+  ${macro.spaces}EXPECT_FALSE(${macro.listItemVarName}.at(${foreach.index}).has_value());
+#else
+  ${macro.spaces}EXPECT_TRUE(${macro.listItemVarName}.at(${foreach.index}).has_value());
+  ${macro.spaces}const ${macro.listMemberShape.name}& ${macro.listItemVarName}Ref = *${macro.listItemVarName}.at(${foreach.index});
+#foreach($innerParam in $arrayItem.fields())
+#ValidateParamsMacro("${macro.spaces}  " "${macro.listItemVarName}Ref" $macro.listMemberShape $innerParam)
+#end
+#end
+${macro.spaces}}
+#end
+#else
 ${macro.spaces}EXPECT_EQ(${testValidateParamVal.size()}U, ${dstObject}.${macro.fieldGetter}.size());
 #foreach($arrayItem in $testValidateParamVal)
 ${macro.spaces}{
@@ -47,11 +64,25 @@ ${macro.spaces}{
 #end##list
 ${macro.spaces}}
 #end##foreach
+#end
 #else## not (list || map || structure)
+#if($listShape.sparse)
+${macro.spaces}const Aws::Vector<Aws::Crt::Optional<$CppViewHelper.computeCppType($macro.listMemberShape)>>& $macro.listItemVarName = ${dstObject}.${macro.fieldGetter};
+${macro.spaces}EXPECT_EQ(${testValidateParamVal.size()}U, ${macro.listItemVarName}.size());
+#foreach($arrayItem in $testValidateParamVal)
+#if($arrayItem.isNull())
+${macro.spaces}EXPECT_FALSE(${macro.listItemVarName}.at(${foreach.index}).has_value());
+#else
+${macro.spaces}EXPECT_TRUE(${macro.listItemVarName}.at(${foreach.index}).has_value());
+${macro.spaces}EXPECT_EQ(#ValidateSingleParameterMacro($macro.listMemberShape, $arrayItem), *${macro.listItemVarName}.at(${foreach.index}));
+#end
+#end
+#else
 ${macro.spaces}const Aws::Vector<$CppViewHelper.computeCppType($macro.listMemberShape)>& $macro.listItemVarName = ${dstObject}.${macro.fieldGetter};
 ${macro.spaces}EXPECT_EQ(${testValidateParamVal.size()}U, ${macro.listItemVarName}.size());
 #foreach($arrayItem in $testValidateParamVal)
 ${macro.spaces}EXPECT_EQ(#ValidateSingleParameterMacro($macro.listMemberShape, $arrayItem), ${macro.listItemVarName}.at(${foreach.index}));
 #end
+#end##sparse
 #end##(list || map || structure)
 #end##macro ValidateListMacro
\ No newline at end of file
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateMapMacro.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateMapMacro.vm
index 845748270b70..0bb3482a8fe2 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateMapMacro.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateMapMacro.vm
@@ -25,6 +25,24 @@ ${macro.spaces}EXPECT_STREQ(R"j(${mapItem.value})j", ${macro.mapVarName}.at("$ma
 #break
 #end
 #if($mapShape.mapValue.shape.structure)
+#if($mapShape.sparse)
+${macro.spaces}const Aws::Map<$CppViewHelper.computeCppType($mapShape.mapKey.shape), Aws::Crt::Optional<$CppViewHelper.computeCppType($mapShape.mapValue.shape)>>& $macro.mapVarName = ${dstObject}.${macro.fieldGetter};
+${macro.spaces}EXPECT_EQ(${testValidateParamVal.size()}U, ${macro.mapVarName}.size());
+#foreach($mapItem in $testValidateParamVal.fields())
+${macro.spaces}{
+  ${macro.spaces}EXPECT_TRUE(${macro.mapVarName}.find("$mapItem.key") != ${macro.mapVarName}.end());
+#if($mapItem.value.isNull())
+  ${macro.spaces}EXPECT_FALSE(${macro.mapVarName}.at("$mapItem.key").has_value());
+#else
+  ${macro.spaces}EXPECT_TRUE(${macro.mapVarName}.at("$mapItem.key").has_value());
+  ${macro.spaces}const $CppViewHelper.computeCppType($mapShape.mapValue.shape)& $macro.mapItemVarName = *${macro.mapVarName}.at("$mapItem.key");
+#foreach($innerParam in $mapItem.value.fields())
+#ValidateParamsMacro("${macro.spaces}  " $macro.mapItemVarName $mapShape.mapValue.shape $innerParam)
+#end
+#end
+${macro.spaces}}
+#end
+#else
 ${macro.spaces}const Aws::Map<$CppViewHelper.computeCppType($mapShape.mapKey.shape), $CppViewHelper.computeCppType($mapShape.mapValue.shape)>& $macro.mapVarName = ${dstObject}.${macro.fieldGetter};
 ${macro.spaces}EXPECT_EQ(${testValidateParamVal.size()}U, ${macro.mapVarName}.size());
 #foreach($mapItem in $testValidateParamVal.fields())
@@ -36,9 +54,23 @@ ${macro.spaces}{
 #end
 ${macro.spaces}}
 #end
+#end
 #break
 #end
 ###----- the map value is not nested structure or document
+#if($mapShape.sparse)
+${macro.spaces}const Aws::Map<$CppViewHelper.computeCppType($mapShape.mapKey.shape), Aws::Crt::Optional<$CppViewHelper.computeCppType($mapShape.mapValue.shape)>>& $macro.mapVarName = ${dstObject}.${macro.fieldGetter};
+${macro.spaces}EXPECT_EQ(${testValidateParamVal.size()}U, ${macro.mapVarName}.size());
+#foreach($mapItem in $testValidateParamVal.fields())
+${macro.spaces}EXPECT_TRUE(${macro.mapVarName}.find("$mapItem.key") != ${macro.mapVarName}.end());
+#if($mapItem.value.isNull())
+${macro.spaces}EXPECT_FALSE(${macro.mapVarName}.at("$mapItem.key").has_value());
+#else
+${macro.spaces}EXPECT_TRUE(${macro.mapVarName}.at("$mapItem.key").has_value());
+${macro.spaces}EXPECT_EQ(#ValidateSingleParameterMacro($mapShape.mapValue.shape, $mapItem.value), *${macro.mapVarName}.at("$mapItem.key"));
+#end
+#end
+#else
 ${macro.spaces}const Aws::Map<$CppViewHelper.computeCppType($mapShape.mapKey.shape), $CppViewHelper.computeCppType($mapShape.mapValue.shape)>& $macro.mapVarName = ${dstObject}.${macro.fieldGetter};
 ${macro.spaces}EXPECT_EQ(${testValidateParamVal.size()}U, ${macro.mapVarName}.size());
 #foreach($mapItem in $testValidateParamVal.fields())
@@ -48,4 +80,5 @@ ${macro.spaces}EXPECT_TRUE(${macro.mapVarName}.find("$mapItem.key") != ${macro.m
 #set($macro.var = $macro.mapItemVarName)
 #ValidateSingleVariableMacro($macro.spaces, $mapShape.mapValue.shape, $mapItem.value, $macro.parentVarName, $macro.getter, $macro.var)
 #end
+#end##sparse
 #end##macro ValidateMapMacro
\ No newline at end of file
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateSingleParameterMacro.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateSingleParameterMacro.vm
index 1e5ee6442cd1..d90493ed1b35 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateSingleParameterMacro.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/protocoltests/result/ValidateSingleParameterMacro.vm
@@ -38,8 +38,7 @@ Aws::Utils::DateTime(static_cast<int64_t>(${value}))##
 #elseif($shape.enum)
 ${shape.name}Mapper::Get${shape.name}ForName(R"e(${value.asText()})e")##
 #elseif($shape.list)
-#set($macro.listResult="Aws::Vector<$CppViewHelper.computeCppType($shape)>({")
-#foreach($listItem in $value)
+#set($macro.listResult="Aws::Vector<$CppViewHelper.computeCppType($shape.listMember.shape)>({")#foreach($listItem in $value)
 #set($macro.listResult=$macro.listResult + "#ValidateSingleParameterMacro($shape.listMember.shape, $listItem)")
 #if($foreach.hasNext)#set($macro.listResult=$macro.listResult + ", ")#end
 #end
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeRequestQueryListElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeRequestQueryListElement.vm
index 03c8ca9e6bab..f4e686065506 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeRequestQueryListElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeRequestQueryListElement.vm
@@ -45,10 +45,23 @@
 #end
 #end
 #if($member.shape.listMember.shape.structure)
+#if($member.shape.sparse)
+  ${macro.spaces}  if(item.has_value()) {
+  ${macro.spaces}    item.value().OutputToStream(ss, "${macro.listLocation}.", ${varName}Count, "");
+  ${macro.spaces}  }
+#else
   ${macro.spaces}  item.OutputToStream(ss, "${macro.listLocation}.", ${varName}Count, "");
+#end
+#else
+#if($member.shape.sparse)
+  ${macro.spaces}  if(item.has_value()) {
+  ${macro.spaces}    ss << "${macro.listLocation}." << ${varName}Count << "="
+  ${macro.spaces}        << #serializeQuerySingleElementToText($macro.spaces, $member.shape.listMember, "item.value()") << "&";
+  ${macro.spaces}  }
 #else
   ${macro.spaces}  ss << "${macro.listLocation}." << ${varName}Count << "="
   ${macro.spaces}      << #serializeQuerySingleElementToText($macro.spaces, $member.shape.listMember, "item") << "&";
+#end
 #end
   ${macro.spaces}  ${varName}Count++;
   ${macro.spaces}}
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeRequestQueryMapElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeRequestQueryMapElement.vm
index 751eca7c55ab..f797d4abb67a 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeRequestQueryMapElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeRequestQueryMapElement.vm
@@ -35,14 +35,27 @@
 #end
 ## --- MAP VALUE ---
 #if($member.shape.mapValue.shape.structure)
+#if($member.shape.sparse)
+  ${spaces}  if(item.second.has_value()) {
+  ${spaces}    item.second.value().OutputToStream(ss, "${macro.mapLocationName}.", ${macro.varName}Count, ".${macro.valueLocationName}");
+  ${spaces}  }
+#else
   ${spaces}  item.second.OutputToStream(ss, "${macro.mapLocationName}.", ${macro.varName}Count, ".${macro.valueLocationName}");
+#end
 #else
 #set($macro.equals='=')
 #if($member.shape.mapValue.shape.list || $member.shape.mapValue.shape.map)
 #set($macro.equals='')
 #end
+#if($member.shape.sparse)
+  ${spaces}    if(item.second.has_value()) {
+  ${spaces}      ss << "${macro.mapLocationName}." << ${macro.varName}Count << ".${macro.valueLocationName}${macro.equals}"
+  ${spaces}          << #serializeQuerySingleElementToText($spaces, $member.shape.mapValue, "item.second.value()") << "&";
+  ${spaces}    }
+#else
   ${spaces}  ss << "${macro.mapLocationName}." << ${macro.varName}Count << ".${macro.valueLocationName}${macro.equals}"
   ${spaces}      << #serializeQuerySingleElementToText($spaces, $member.shape.mapValue, "item.second") << "&";
+#end
 #end
   ${spaces}  ${macro.varName}Count++;
   ${spaces}}
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeSubObjQueryMapElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeSubObjQueryMapElement.vm
index 633eddb064d3..4db390fc41b7 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeSubObjQueryMapElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/queryxml/QuerySerializeTemplateMacros/serializeSubObjQueryMapElement.vm
@@ -32,14 +32,26 @@
 #if($member.shape.mapValue.shape.structure)
   ${spaces}  Aws::StringStream ${macro.lowerCaseVarName}Ss;
   ${spaces}  ${macro.lowerCaseVarName}Ss << location << ${macro.locationIndexValue}".${macro.mapLocationName}." << ${macro.lowerCaseVarName}Idx << ".${macro.mapValueLocationName}";
+#if($member.shape.sparse)
+  ${spaces}  if(item.second.has_value()) {
+  ${spaces}    item.second.value().OutputToStream(oStream, ${macro.lowerCaseVarName}Ss.str().c_str());
+  ${spaces}  }
+#else
   ${spaces}  item.second.OutputToStream(oStream, ${macro.lowerCaseVarName}Ss.str().c_str());
+#end
 #else
 #set($macro.equals='="')
 #if($member.shape.mapValue.shape.list || $member.shape.mapValue.shape.map)
 #set($macro.equals='"')
 #end
 #set($mapValueLocation = '".' + "${macro.mapLocationName}." + '"' + " << ${macro.lowerCaseVarName}Idx << " + '".' + ${macro.mapValueLocationName} + $macro.equals + $nl + "  ${spaces}     ")
+#if($member.shape.sparse)
+  ${spaces}  if(item.second.has_value()) {
+  ${spaces}    oStream << location << ${macro.locationIndexValue}#serializeSubObjQuerySingleElement($member.shape.mapValue, $mapValueLocation, "item.second.value()") << "&";
+  ${spaces}  }
+#else
   ${spaces}  oStream << location << ${macro.locationIndexValue}#serializeSubObjQuerySingleElement($member.shape.mapValue, $mapValueLocation, "item.second") << "&";
+#end
 #end
   ${spaces}  ${macro.lowerCaseVarName}Idx++;
   ${spaces}}
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlListPayloadElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlListPayloadElement.vm
index 289c96de1220..be8e43a22dbf 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlListPayloadElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlListPayloadElement.vm
@@ -54,7 +54,19 @@
     ${macro.spaces}while(!${macro.listVarName}.IsNull())
     ${macro.spaces}{
 #set($macro.memberVarName = $CppViewHelper.computeMemberVariableName($memberName))
+#if($member.shape.sparse)
+    ${macro.spaces}  if(${macro.listVarName}.GetText().empty() || ${macro.listVarName}.GetAttributeValue("xsi:nil") == "true") { 
+    ${macro.spaces}    ${macro.memberVarName}.emplace_back(); 
+    ${macro.spaces}  } else { 
+#if($member.shape.listMember.shape.structure)
+    ${macro.spaces}    ${macro.memberVarName}.emplace_back(#deserializeXmlSingleElement($member.shape.listMember, $macro.listVarName)); 
+#else
+    ${macro.spaces}    ${macro.memberVarName}.push_back(#deserializeXmlSingleElement($member.shape.listMember, $macro.listVarName)); 
+#end
+    ${macro.spaces}  }
+#else
     ${macro.spaces}  ${macro.memberVarName}.push_back(#deserializeXmlSingleElement($member.shape.listMember, $macro.listVarName));
+#end
 #if($member.shape.listMember.locationName)
 #set($listMemberName = $member.shape.listMember.locationName)
 #elseif(!($member.shape.flattened || $member.flattened))
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlMapPayloadElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlMapPayloadElement.vm
index c117ed91570a..1c3ed3ccc637 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlMapPayloadElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlMapPayloadElement.vm
@@ -38,8 +38,14 @@
     ${macro.spaces}  XmlNode valueNode = ${macro.mapVarName}.FirstChild("value");
 #end
 #set($macro.memberVarName = $CppViewHelper.computeMemberVariableName($memberName))
+#if($member.shape.sparse)
+    ${macro.spaces}  if(valueNode.IsNull() || valueNode.GetAttributeValue("xsi:nil") == "true") { ${macro.memberVarName}[#deserializeXmlSingleElement($member.shape.mapKey, "keyNode")]; } else {
+    ${macro.spaces}  ${macro.memberVarName}[#deserializeXmlSingleElement($member.shape.mapKey, "keyNode")] =
+    ${macro.spaces}      #deserializeXmlSingleElement($member.shape.mapValue, "valueNode", $macro.spaces, false); }
+#else
     ${macro.spaces}  ${macro.memberVarName}[#deserializeXmlSingleElement($member.shape.mapKey, "keyNode")] =
     ${macro.spaces}      #deserializeXmlSingleElement($member.shape.mapValue, "valueNode", $macro.spaces, false);
+#end
 #if($member.locationName)
     ${macro.spaces}  ${macro.mapVarName} = ${macro.mapVarName}.NextNode("${member.locationName}");
 #else
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlNestedListElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlNestedListElement.vm
index f04e717dbbb3..015c9b215b24 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlNestedListElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlNestedListElement.vm
@@ -8,7 +8,15 @@
     ${macro.spaces}  if(${memberVarName}.IsNull())  { return ${macro.resultVarName}; }
     ${macro.spaces}  XmlNode ${macro.resultVarName}MemberNode = ${memberVarName}.FirstChild("${CppViewHelper.ifNotNullOrEmpty($member.locationName, 'member')}");
     ${macro.spaces}  while(!${macro.resultVarName}MemberNode.IsNull()) {
+#if($member.shape.sparse)
+    ${macro.spaces}    if(${macro.resultVarName}MemberNode.IsNull() || ${macro.resultVarName}MemberNode.GetText().empty()) {
+    ${macro.spaces}      ${macro.resultVarName}.push_back(Aws::Crt::Optional<$CppViewHelper.computeCppType($member.shape.listMember.shape)>{});
+    ${macro.spaces}    } else {
+    ${macro.spaces}      ${macro.resultVarName}.push_back(#deserializeXmlSingleElement($member.shape.listMember, "${macro.resultVarName}MemberNode"));
+    ${macro.spaces}    }
+#else
     ${macro.spaces}    ${macro.resultVarName}.push_back(#deserializeXmlSingleElement($member.shape.listMember, "${macro.resultVarName}MemberNode"));
+#end
     ${macro.spaces}    ${macro.resultVarName}MemberNode = ${macro.resultVarName}MemberNode.NextNode("${CppViewHelper.ifNotNullOrEmpty($member.locationName, 'member')}");
     ${macro.spaces}  }
     ${macro.spaces}  return ${macro.resultVarName};
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlNestedMapElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlNestedMapElement.vm
index 2eadbc20f8ec..52ee6eeb9c25 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlNestedMapElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlDeserializeTemplateMacros/deserializeXmlNestedMapElement.vm
@@ -23,8 +23,17 @@
     ${macro.spaces}  while(!${macro.resultVarName}EntryNode.IsNull()) {
     ${macro.spaces}    XmlNode ${macro.resultVarName}KeyNode = ${macro.resultVarName}EntryNode.FirstChild("${CppViewHelper.ifNotNullOrEmpty($member.shape.mapKey.locationName, 'key')}");
     ${macro.spaces}    XmlNode ${macro.resultVarName}ValNode = ${macro.resultVarName}EntryNode.FirstChild("${CppViewHelper.ifNotNullOrEmpty($member.shape.mapValue.locationName, 'value')}");
+#if($member.shape.sparse)
+    ${macro.spaces}    if(${macro.resultVarName}ValNode.IsNull() || ${macro.resultVarName}ValNode.GetText().empty()) {
+    ${macro.spaces}      ${macro.resultVarName}[#deserializeXmlSingleElement($member.shape.mapKey, "${macro.resultVarName}KeyNode")] = Aws::Crt::Optional<$CppViewHelper.computeCppType($member.shape.mapValue.shape)>{};
+    ${macro.spaces}    } else {
+    ${macro.spaces}      ${macro.resultVarName}[#deserializeXmlSingleElement($member.shape.mapKey, "${macro.resultVarName}KeyNode")] =
+    ${macro.spaces}          #deserializeXmlSingleElement($member.shape.mapValue, "${macro.resultVarName}ValNode", $macro.spaces, false);
+    ${macro.spaces}    }
+#else
     ${macro.spaces}    ${macro.resultVarName}[#deserializeXmlSingleElement($member.shape.mapKey, "${macro.resultVarName}KeyNode")] =
     ${macro.spaces}        #deserializeXmlSingleElement($member.shape.mapValue, "${macro.resultVarName}ValNode", $macro.spaces, false);
+#end
     ${macro.spaces}    ${macro.resultVarName}EntryNode = ${macro.resultVarName}EntryNode.NextNode("${CppViewHelper.ifNotNullOrEmpty($member.locationName, 'entry')}");
     ${macro.spaces}  }
     ${macro.spaces}  return ${macro.resultVarName};
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlSerializeTemplateMacros/serializeXmlListPayloadElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlSerializeTemplateMacros/serializeXmlListPayloadElement.vm
index cacc0d8899a9..a046ef956287 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlSerializeTemplateMacros/serializeXmlListPayloadElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlSerializeTemplateMacros/serializeXmlListPayloadElement.vm
@@ -29,6 +29,15 @@
 ## if list is flattened than the name of repeated XML element is ShapeMember name in parent name OR explicitly set by parent's locationName
 #set($macro.listMemberSerializationName = ${CppViewHelper.ifNotNullOrEmpty($member.locationName, $serializationName)})
 #end
+#if($member.shape.sparse)
+  ${spaces}  if(!${macro.listItemVarName}.has_value()) {
+  ${spaces}    XmlNode ${lowerCaseVarName}NilNode = ${macro.listMemberParentNode}.CreateChildElement("${macro.listMemberSerializationName}");
+  ${spaces}    ${lowerCaseVarName}NilNode.SetAttributeValue("xsi:nil", "true");
+  ${spaces}  } else {
+#serializeXmlSinglePayloadElement($macro.listSpaces, $macro.listMemberSerializationName, $lowerCaseVarName, $member.shape.listMember, "(*${macro.listItemVarName})", $macro.listMemberParentNode)
+  ${spaces}  }
+#else
 #serializeXmlSinglePayloadElement($macro.listSpaces, $macro.listMemberSerializationName, $lowerCaseVarName, $member.shape.listMember, $macro.listItemVarName, $macro.listMemberParentNode)
+#end
   ${spaces}}
 #end##macro serializeXmlListPayloadElement
\ No newline at end of file
diff --git a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlSerializeTemplateMacros/serializeXmlMapPayloadElement.vm b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlSerializeTemplateMacros/serializeXmlMapPayloadElement.vm
index abd754414e4a..23fa939fe361 100644
--- a/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlSerializeTemplateMacros/serializeXmlMapPayloadElement.vm
+++ b/tools/code-generation/generator/src/main/resources/com/amazonaws/util/awsclientgenerator/velocity/cpp/xml/XmlSerializeTemplateMacros/serializeXmlMapPayloadElement.vm
@@ -25,6 +25,15 @@
 #set($macro.mapKeySerializationName = "#if($member.shape.mapKey.locationName)$member.shape.mapKey.locationName#{else}key#end")
 #serializeXmlSinglePayloadElement($macro.mapSpaces, $macro.mapKeySerializationName, "${lowerCaseVarName}Key", $member.shape.mapKey, "${macro.mapItemVarName}.first", "${lowerCaseVarName}MapEntryNode")
 #set($macro.mapValueSerializationName = "#if($member.shape.mapValue.locationName)$member.shape.mapValue.locationName#{else}value#end")
+#if($member.shape.sparse)
+  ${spaces}  if(!${macro.mapItemVarName}.second.has_value()) {
+  ${spaces}    XmlNode ${lowerCaseVarName}NilNode = ${lowerCaseVarName}MapEntryNode.CreateChildElement("${macro.mapValueSerializationName}");
+  ${spaces}    ${lowerCaseVarName}NilNode.SetAttributeValue("xsi:nil", "true");
+  ${spaces}  } else {
+#serializeXmlSinglePayloadElement($macro.mapSpaces, $macro.mapValueSerializationName, "${lowerCaseVarName}Value", $member.shape.mapValue, "(*${macro.mapItemVarName}.second)", "${lowerCaseVarName}MapEntryNode")
+  ${spaces}  }
+#else
 #serializeXmlSinglePayloadElement($macro.mapSpaces, $macro.mapValueSerializationName, "${lowerCaseVarName}Value", $member.shape.mapValue, "${macro.mapItemVarName}.second", "${lowerCaseVarName}MapEntryNode")
+#end
   ${spaces}}
 #end##macro serializeXmlMapPayloadElement
\ No newline at end of file
diff --git a/tools/scripts/run_code_generation.py b/tools/scripts/run_code_generation.py
index 29b8e9986389..a90bd4422459 100644
--- a/tools/scripts/run_code_generation.py
+++ b/tools/scripts/run_code_generation.py
@@ -156,7 +156,10 @@ def main():
             return -1
 
         if args["generate_protocol_tests"]:
-            protocol_tests_generator = ProtocolTestsGen(args)
+            # Disable smithy generation for protocol tests
+            protocol_args = args.copy()
+            protocol_args["disable_smithy_generation"] = True
+            protocol_tests_generator = ProtocolTestsGen(protocol_args)
             if protocol_tests_generator.generate(executor, max_workers) != 0:
                 print("ERROR: Failed to generate protocol test(s)!")
                 return -1