error-handling-patterns

Extend a base AppError class that captures statusCode, error code, and stack trace, then create specific subclasses like ValidationError or NotFoundError. This gives type-safe errors with consistent HTTP status codes across your API.

Wrap async route handlers in an asyncHandler function that forwards rejected promises to next(), or import express-async-errors to catch them automatically. Then a centralized error middleware formats all errors into consistent JSON responses.

A circuit breaker tracks failure counts and stops calling a failing service after a threshold, entering an OPEN state for a timeout period. After the timeout it allows a trial request (HALF_OPEN) to check if the service recovered.

No, error boundaries only catch errors during rendering, in lifecycle methods, and in constructors. Async errors in event handlers or useEffect must be caught with try/catch and stored in state to display fallback UI.

Use exponential backoff for transient failures like network timeouts or rate-limited external API calls. Double the delay between attempts up to a maximum, and avoid retrying non-transient errors like validation failures.