Worked on the guardian/dotcom-rendering repository to deliver a caching layer for newsletter subscriptions, targeting improved performance and reduced backend load for unsigned and signed-out users. The implementation involved developing precise cache invalidation logic that clears stored data upon user sign-out and when rendering pages for users not signed in, ensuring data freshness and reliability. Expanded automated tests to cover caching behavior, invalidation flows, and cache refresh scenarios, validating the robustness of the solution. Utilized React for front end development, leveraging state management techniques and working primarily with JavaScript and TypeScript to maintain code quality and maintainability throughout the project.