From latency to instant: Modernizing GitHub Issues navigation performance

This 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).