API On Point

What an API is; HTTP requests; HTTP responses; RESTful design; response structure; MongoDB; Node.js; Express; CORS; authentication; next steps.

An API is a contract and boundary, not merely a URL.
Requests combine method, path, headers, query, and body; responses combine status, headers, and representation.
Use resource-oriented URLs and HTTP semantics consistently, but model domain actions honestly when CRUD is insufficient.
Status codes and error bodies should let clients distinguish invalid, unauthenticated, forbidden, missing, conflicting, and failed operations.
Validate every external input and authorize access at the resource/action level.
CORS is a browser permission mechanism, not authentication or server-side access control.
Stable APIs require pagination, idempotency, rate limits, timeouts, version/evolution strategy, documentation, and observability.