Most web apps freeze for hundreds of milliseconds during updates, but Linear responds in just a few milliseconds. The secret lies in inverting the traditional client-server relationship. Instead of waiting for HTTP requests to complete, Linear treats the browser as the primary database using IndexedDB for local storage, applying mutations immediately and syncing with the server asynchronously in the background.

Network latency becomes the biggest bottleneck for web app performance. Linear eliminates this by making UI responsiveness independent of server responses. When a user updates an issue, the change applies to local state instantly, triggering immediate re-renders without spinners or loading states. The sync engine batches transactions and pushes them to the server via WebSocket, while other clients receive deltas in real-time. This optimistic update approach prioritizes perceived speed over actual server response time.

Linear's commitment to performance extends to their build pipeline, which they've rebuilt four times: Parcel to Rollup to Vite to Rolldown. Each migration targeted the same goal—shipping less JavaScript and CSS. Their blog claims 50% less code shipped, 30% smaller bundles after compression, and a 59% improvement in Safari's time-to-first-paint for the active-issues view.

The stack remains remarkably simple: React, TypeScript, MobX, PostgreSQL, and a CDN. No edge databases or React Server Components needed. By dropping legacy browser support and implementing aggressive code splitting, Linear proves that architectural decisions matter more than framework choices. Performance optimization starts at build time, not runtime.