imlazy-api-design

API Design Patterns

Conventions and best practices for designing consistent, developer-friendly REST APIs.

When to Activate

• Designing new API endpoints
• Reviewing existing API contracts
• Adding pagination, filtering, or sorting
• Implementing error handling for APIs
• Planning API versioning strategy
• Building public or partner-facing APIs

Resource Design

URL Structure

# Resources are nouns, plural, lowercase, kebab-case
GET    /api/v1/users
GET    /api/v1/users/:id
POST   /api/v1/users
PUT    /api/v1/users/:id
PATCH  /api/v1/users/:id
DELETE /api/v1/users/:id

# Sub-resources for relationships
GET    /api/v1/users/:id/orders
POST   /api/v1/users/:id/orders

# Actions that don't map to CRUD (use verbs sparingly)
POST   /api/v1/orders/:id/cancel
POST   /api/v1/auth/login
POST   /api/v1/auth/refresh

Naming Rules

# GOOD
/api/v1/team-members          # kebab-case for multi-word resources
/api/v1/orders?status=active  # query params for filtering
/api/v1/users/123/orders      # nested resources for ownership

# BAD
/api/v1/getUsers              # verb in URL
/api/v1/user                  # singular (use plural)
/api/v1/team_members          # snake_case in URLs
/api/v1/users/123/getOrders   # verb in nested resource

HTTP Methods and Status Codes

Method Semantics

Method	Idempotent	Safe	Use For
GET	Yes	Yes	Retrieve resources
POST	No	No	Create resources, trigger actions
PUT	Yes	No	Full replacement of a resource
PATCH	No*	No	Partial update of a resource
DELETE	Yes	No	Remove a resource

*PATCH can be made idempotent with proper implementation

Status Code Reference

# Success
200 OK                    — GET, PUT, PATCH (with response body)
201 Created               — POST (include Location header)
204 No Content            — DELETE, PUT (no response body)

# Client Errors
400 Bad Request           — Validation failure, malformed JSON
401 Unauthorized          — Missing or invalid authentication
403 Forbidden             — Authenticated but not authorized
404 Not Found             — Resource doesn't exist
409 Conflict              — Duplicate entry, state conflict
422 Unprocessable Entity  — Semantically invalid (valid JSON, bad data)
429 Too Many Requests     — Rate limit exceeded

# Server Errors
500 Internal Server Error — Unexpected failure (never expose details)
502 Bad Gateway           — Upstream service failed
503 Service Unavailable   — Temporary overload, include Retry-After