From 7b57f495722a766fa9d0869a376d3811630a9074 Mon Sep 17 00:00:00 2001
From: Morgan Roderick <morgan@roderick.dk>
Date: Thu, 17 Sep 2026 11:05:50 +0200
Subject: [PATCH 1/2] Cache the rendered /sponsors page body

Cache the rendered page in the shared cache store, keyed on
"sponsors/index/v1/#{Sponsor.active.maximum(:updated_at)&.to_fs(:usec)}",
so a warm request costs one cache read instead of re-rendering 721
sponsor fragments (~1.3s CPU-bound per render). Solid Cache is
DB-backed, so the body also survives deploys and dyno restarts.

The key is computed before the records load so a save committing
between the two queries self-heals on the next request, and the v1
segment lets a reviewer invalidate the body when the view changes.
---
 app/controllers/sponsors_controller.rb |  6 ++++
 spec/requests/sponsors_spec.rb         | 43 ++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)
 create mode 100644 spec/requests/sponsors_spec.rb

diff --git a/app/controllers/sponsors_controller.rb b/app/controllers/sponsors_controller.rb
index 40cd41b1c..64db3a955 100644
--- a/app/controllers/sponsors_controller.rb
+++ b/app/controllers/sponsors_controller.rb
@@ -1,5 +1,11 @@
 class SponsorsController < ApplicationController
   def index
+    # v1: bump when the sponsors view or partials change, otherwise a deploy
+    # keeps serving the cached body until the next sponsor save.
+    key = "sponsors/index/v1/#{Sponsor.active.maximum(:updated_at)&.to_fs(:usec)}"
     @sponsor_levels = Sponsor.active.group_by(&:level)
+    body = Rails.cache.fetch(key) { render_to_string(layout: false) }
+    # body is markup rendered by this app's own template, not user input
+    render html: body.html_safe # rubocop:disable Rails/OutputSafety
   end
 end
diff --git a/spec/requests/sponsors_spec.rb b/spec/requests/sponsors_spec.rb
new file mode 100644
index 000000000..6e8a75bec
--- /dev/null
+++ b/spec/requests/sponsors_spec.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Sponsors' do
+  let!(:sponsor) { Fabricate.create(:sponsor, name: 'Acme Corp') }
+
+  around do |example|
+    original_cache = Rails.cache
+    Rails.cache = ActiveSupport::Cache::MemoryStore.new
+    example.run
+    Rails.cache = original_cache
+  end
+
+  it 'renders the sponsors page' do
+    get '/sponsors'
+
+    expect(response).to have_http_status(:ok)
+    expect(response.body).to include('Acme Corp')
+  end
+
+  it 'serves the cached body when no sponsor has been updated' do
+    get '/sponsors'
+
+    # update_columns bypasses callbacks, so updated_at (and the cache key) stays unchanged
+    sponsor.update_columns(name: 'Renamed Corp')
+
+    get '/sponsors'
+
+    expect(response.body).to include('Acme Corp')
+    expect(response.body).not_to include('Renamed Corp')
+  end
+
+  it 're-renders when a sponsor is updated' do
+    get '/sponsors'
+
+    sponsor.update!(name: 'Renamed Corp')
+
+    get '/sponsors'
+
+    expect(response.body).to include('Renamed Corp')
+  end
+end

From 5d01c78b601c6b4582acdec929b013076598991a Mon Sep 17 00:00:00 2001
From: Morgan Roderick <morgan@roderick.dk>
Date: Sat, 19 Sep 2026 13:57:01 +0200
Subject: [PATCH 2/2] Move the sponsor load inside the cache block

Warm requests no longer instantiate 721 AR objects they never use; the
load only runs on a cache miss, so the warm path is one `maximum` query
plus one cache read. Matches the corrected proposal in #2885.
---
 app/controllers/sponsors_controller.rb | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/app/controllers/sponsors_controller.rb b/app/controllers/sponsors_controller.rb
index 64db3a955..6452091b6 100644
--- a/app/controllers/sponsors_controller.rb
+++ b/app/controllers/sponsors_controller.rb
@@ -3,8 +3,10 @@ def index
     # v1: bump when the sponsors view or partials change, otherwise a deploy
     # keeps serving the cached body until the next sponsor save.
     key = "sponsors/index/v1/#{Sponsor.active.maximum(:updated_at)&.to_fs(:usec)}"
-    @sponsor_levels = Sponsor.active.group_by(&:level)
-    body = Rails.cache.fetch(key) { render_to_string(layout: false) }
+    body = Rails.cache.fetch(key) do
+      @sponsor_levels = Sponsor.active.group_by(&:level)
+      render_to_string(layout: false)
+    end
     # body is markup rendered by this app's own template, not user input
     render html: body.html_safe # rubocop:disable Rails/OutputSafety
   end