Web + frameworks / Intermediate

HTTP, REST APIs, and backend design

Requests, responses, status codes, JSON APIs, validation, idempotency, pagination, authentication, and API boundaries.

httprestapijsonbackend

01HTTP model

Method	Typical purpose
GET	Read without changing state
POST	Create/command
PUT	Replace resource
PATCH	Partial update
DELETE	Delete resource

The method, path, headers, body, authentication context, and server state determine a request. The response includes a status code, headers, and usually a representation such as JSON or HTML.

02Status codes

200/201: successful read/create.
204: success with no response body.
400: malformed or invalid request.
401: authentication required/invalid.
403: authenticated but not authorized.
404: resource not found.
409: state conflict.
422: semantically invalid input when your API convention uses it.
429: rate limited.
500: unexpected server failure.

03Small Flask JSON endpoint

pythonRead-only endpoint

@bp.get('/api/projects')
def api_projects():
    rows = Project.query.filter_by(published=True).all()
    return {
        'projects': [
            {'slug': row.slug, 'name': row.name}
            for row in rows
        ]
    }