2. APIs & Backend Design
Error Handling & Failure Boundaries
Build errors that are safe for users, useful for developers and consistent across APIs and workers.
Lesson overview
Errors are part of the API contract. Separate validation and permission failures from infrastructure failures, return stable error codes, and log internal detail with correlation IDs instead of exposing stack traces.
Learning path
Theory → Example → Code → Practice → Quiz → Challenge → Completion
Step 1
Theory
Errors are part of the API contract. Separate validation and permission failures from infrastructure failures, return stable error codes, and log internal detail with correlation IDs instead of exposing stack traces.
Step 2
Example
A product API can return VALIDATION_ERROR for malformed input and DEPENDENCY_TIMEOUT for a provider failure while logging the provider exception internally.
Step 3
Code
typescript
return Response.json(
{ code: "DEPENDENCY_TIMEOUT", requestId },
{ status: 503 },
);
Step 4
Practice
Review your current application and apply Error Handling & Failure Boundaries. Document the current behavior, one production risk, the change you would make, and how you would verify it.
Step 5
Quiz
1. What is the central production concern in "Error Handling & Failure Boundaries"?
Step 6
Challenge
Design a production-ready implementation for Error Handling & Failure Boundaries. Include failure handling, security considerations, observability, testing and a rollback or recovery path where applicable.
Complete every stage
Work through every step in order, then the lesson will be marked complete.
Each chapter and subtopic has its own public URL under /full-stack-to-production.