Error boundaries -- isolate failures to preserve functionality

One failing component or service takes down the entire application. A non-critical widget crash causes the whole page to go blank. A microservice failure causes the entire request to fail.

Wrap independent sections in error boundaries: (1) React: ErrorBoundary components around independent UI sections. (2) Backend: try-catch around non-critical operations, return partial responses. (3) Microservices: circuit breakers + fallback values for non-critical services. (4) Feature flags: disable broken features without deploying. Design for partial failure: the search bar can work even if recommendations are down.

Not all parts of an application are equally important. Isolating failures ensures that a non-critical feature crash does not destroy the critical user experience.