Targeted Query Caching for Expensive Endpoints

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                  class ReportsController < ApplicationController
  def show
    @report = ActiveRecord::Base.cache do
      Reports::Build.new(current_member, params).call
    end
  end
end

                  module Reports
  class Build
    def initialize(member, params)
      @member = member
      @params = params
    end

    def call
      {
        top_projects: Project.visible_to(@member).order(score: :desc).limit(25).to_a,
        recent_comments: Comment.visible_to(@member).order(created_at: :desc).limit(50).to_a
      }
    end
  end
end

I’ve had endpoints where the same lookups get repeated across helpers and partials, and I didn’t want to pay for query caching on every request. In Scoped query cache, I wrap only the expensive report build in ActiveRecord::Base.cache, so the cache lives for the duration of that block and nowhere else. Then, in Report builder, I keep the builder focused on returning structured data and let ActiveRecord reuse the cached queries for calls like Project.visible_to(...).order(...).limit(...) and Comment.visible_to(...).order(...).limit(...). This pattern keeps memory pressure low for the average request, but it still gives me the “one request, one set of queries” behavior on pages that are query-heavy by design. It’s targeted, predictable, and easy to remove if it stops helping.

Sarah Chen

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Targeted Query Caching for Expensive Endpoints

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