HTTP essentials

HTTP is the language of backend work. This class builds the mental model you will use for every service in the program.

The requestCopy Anchor Link

POST /api/v1/auth/login HTTP/1.1
Host: learn.bigiverse.com
Content-Type: application/json
Origin: http://localhost:3001

{"email":"ada@example.com","password":"s3cr3t!"}

The four parts that matter: the verb, the path, the headers, and the body. Every framework you use is just a nicer way of writing this.

The responseCopy Anchor Link

HTTP/1.1 200 OK
Content-Type: application/json
Set-Cookie: bl_session=…; HttpOnly; Path=/; SameSite=Lax

{"data":{"user":{"id":"…"}}}

A healthy status-code habitCopy Anchor Link

• 2xx — it worked. 200 ordinary, 201 created, 204 deleted.
• 4xx — the caller made a mistake. Use 400 for malformed input, 401 for missing login, 403 for doing something you may not, 404 when something does not exist, 409 for conflicts, 422 for validation.
• 5xx — the server made a mistake. 503 when a dependency is down.

Consistency matters more than cleverness: pick a convention and document it (your API contract is exactly that documentation).

The contract is the productCopy Anchor Link

If your frontend and backend are separate applications, the contract between them — this is your OpenAPI document — is a small product of its own. A typed client generated from the contract turns half your runtime bugs into compile-time errors.