Building React applications that scale requires more than knowing hooks and components. It's about architecture, state management, and performance from day one.
Start with a clear folder structure: group by feature or domain rather than by type. Co-locate tests, styles, and utilities with the features they support. This makes it easier for teams to find and change code without stepping on each other.
State management should be intentional. Use local state for UI-only concerns, context sparingly for truly global values, and consider a dedicated store (or server state with React Query) for server data. Avoid prop drilling by keeping state as close as possible to where it's used.
Performance is non-negotiable. Lazy-load routes and heavy components. Memoize expensive computations and list items when necessary. Use the React DevTools Profiler to find real bottlenecks instead of guessing.
Finally, invest in testing and documentation. Well-tested components and clear READMEs pay off when the team grows or when you return to a project after months. Scalability is as much about people as it is about code.