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Client-side Caching for Issues Navigation

2 posts · Jan 2021 – May 2026

What this trail covers

This feature thread tracks the evolution of client-side caching strategies to improve the perceived performance of GitHub Issues navigation. Initially, the focus was on reducing latency for common navigation paths. This post details the implementation of a client-side caching layer backed by IndexedDB, a preheating strategy to improve cache hit rates, and the use of a service worker to maintain cache usability across navigations. The goal is to render issue pages instantly from local data and revalidate in the background, significantly improving the user experience by reducing context switching and making 'fast' the default path for the majority of sessions.

All GitHub trails
  1. From latency to instant: Modernizing GitHub Issues navigation performanceThis post details the implementation of a client-side caching layer for GitHub Issues navigation, backed by IndexedDB, to achieve 'instant' perceived performance. It introduces a stale-while-revalidate strategy for React soft navigations, achieving a ~33% cache-hit ratio and making 22% of navigations instant. It also describes a 'preheating' strategy to proactively populate the cache for high-intent issue references without amplifying request volume, and the use of a service worker to maintain cache usability across navigations. The post discusses tradeoffs, specifically controlled staleness (measured at 4.7% server/cache divergence), and the optimization metric HPC (Highest Priority Content).
  2. Making GitHub’s new homepage fast and performantThis post details two key performance optimization strategies for the GitHub homepage: 1) High-performance animation and interactivity using IntersectionObservers to avoid scroll event listeners and reflows, and explicitly animating only `transform` and `opacity` properties. It also covers lazy-loading videos with IntersectionObservers. 2) Serving the perfect image by leveraging WebP for modern browsers and an SVG-based transparent JPG fallback for older browsers, embedding base64 encoded images within the SVG for a single HTTP request.