REST API design patterns including resource naming, status codes, pagination, filtering, error responses, versioning, and rate limiting for production APIs.
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Skills Directoryopenskills install NomaDamas/girlfriend-in-cli---
name: api-design
description: REST API design patterns including resource naming, status codes, pagination, filtering, error responses, versioning, and rate limiting for production APIs.
origin: ECC
---
# 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
```
### Common Mistakes
```
# BAD: 200 for everything
{ "status": 200, "success": false, "error": "Not found" }
# GOOD: Use HTTP status codes semantically
HTTP/1.1 404 Not Found
{ "error": { "code": "not_found", "message": "User not found" } }
# BAD: 500 for validation errors
# GOOD: 400 or 422 with field-level details
# BAD: 200 for created resources
# GOOD: 201 with Location header
HTTP/1.1 201 Created
Location: /api/v1/users/abc-123
```
## Response Format
### Success Response
```json
{
"data": {
"id": "abc-123",
"email": "alice@example.com",
"name": "Alice",
"created_at": "2025-01-15T10:30:00Z"
}
}
```
### Collection Response (with Pagination)
```json
{
"data": [
{ "id": "abc-123", "name": "Alice" },
{ "id": "def-456", "name": "Bob" }
],
"meta": {
"total": 142,
"page": 1,
"per_page": 20,
"total_pages": 8
},
"links": {
"self": "/api/v1/users?page=1&per_page=20",
"next": "/api/v1/users?page=2&per_page=20",
"last": "/api/v1/users?page=8&per_page=20"
}
}
```
### Error Response
```json
{
"error": {
"code": "validation_error",
"message": "Request validation failed",
"details": [
{
"field": "email",
"message": "Must be a valid email address",
"code": "invalid_format"
},
{
"field": "age",
"message": "Must be between 0 and 150",
"code": "out_of_range"
}
]
}
}
```
### Response Envelope Variants
```typescript
// Option A: Envelope with data wrapper (recommended for public APIs)
interface ApiResponse<T> {
data: T;
meta?: PaginationMeta;
links?: PaginationLinks;
}
interface ApiError {
error: {
code: string;
message: string;
details?: FieldError[];
};
}
// Option B: Flat response (simpler, common for internal APIs)
// Success: just return the resource directly
// Error: return error object
// Distinguish by HTTP status code
```
## Pagination
### Offset-Based (Simple)
```
GET /api/v1/users?page=2&per_page=20
# Implementation
SELECT * FROM users
ORDER BY created_at DESC
LIMIT 20 OFFSET 20;
```
**Pros:** Easy to implement, supports "jump to page N"
**Cons:** Slow on large offsets (OFFSET 100000), inconsistent with concurrent inserts
### Cursor-Based (Scalable)
```
GET /api/v1/users?cursor=eyJpZCI6MTIzfQ&limit=20
# Implementation
SELECT * FROM users
WHERE id > :cursor_id
ORDER BY id ASC
LIMIT 21; -- fetch one extra to determine has_next
```
```json
{
"data": [...],
"meta": {
"has_next": true,
"next_cursor": "eyJpZCI6MTQzfQ"
}
}
```
**Pros:** Consistent performance regardless of position, stable with concurrent inserts
**Cons:** Cannot jump to arbitrary page, cursor is opaque
### When to Use Which
| Use Case | Pagination Type |
|----------|----------------|
| Admin dashboards, small datasets (<10K) | Offset |
| Infinite scroll, feeds, large datasets | Cursor |
| Public APIs | Cursor (default) with offset (optional) |
| Search results | Offset (users expect page numbers) |
## Filtering, Sorting, and Search
### Filtering
```
# Simple equality
GET /api/v1/orders?status=active&customer_id=abc-123
# Comparison operators (use bracket notation)
GET /api/v1/products?price[gte]=10&price[lte]=100
GET /api/v1/orders?created_at[after]=2025-01-01
# Multiple values (comma-separated)
GET /api/v1/products?category=electronics,clothing
# Nested fields (dot notation)
GET /api/v1/orders?customer.country=US
```
### Sorting
```
# Single field (prefix - for descending)
GET /api/v1/products?sort=-created_at
# Multiple fields (comma-separated)
GET /api/v1/products?sort=-featured,price,-created_at
```
### Full-Text Search
```
# Search query parameter
GET /api/v1/products?q=wireless+headphones
# Field-specific search
GET /api/v1/users?email=alice
```
### Sparse Fieldsets
```
# Return only specified fields (reduces payload)
GET /api/v1/users?fields=id,name,email
GET /api/v1/orders?fields=id,total,status&include=customer.name
```
## Authentication and Authorization
### Token-Based Auth
```
# Bearer token in Authorization header
GET /api/v1/users
Authorization: Bearer eyJhbGciOiJIUzI1NiIs...
# API key (for server-to-server)
GET /api/v1/data
X-API-Key: sk_live_abc123
```
### Authorization Patterns
```typescript
// Resource-level: check ownership
app.get("/api/v1/orders/:id", async (req, res) => {
const order = await Order.findById(req.params.id);
if (!order) return res.status(404).json({ error: { code: "not_found" } });
if (order.userId !== req.user.id) return res.status(403).json({ error: { code: "forbidden" } });
return res.json({ data: order });
});
// Role-based: check permissions
app.delete("/api/v1/users/:id", requireRole("admin"), async (req, res) => {
await User.delete(req.params.id);
return res.status(204).send();
});
```
## Rate Limiting
### Headers
```
HTTP/1.1 200 OK
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 95
X-RateLimit-Reset: 1640000000
# When exceeded
HTTP/1.1 429 Too Many Requests
Retry-After: 60
{
"error": {
"code": "rate_limit_exceeded",
"message": "Rate limit exceeded. Try again in 60 seconds."
}
}
```
### Rate Limit Tiers
| Tier | Limit | Window | Use Case |
|------|-------|--------|----------|
| Anonymous | 30/min | Per IP | Public endpoints |
| Authenticated | 100/min | Per user | Standard API access |
| Premium | 1000/min | Per API key | Paid API plans |
| Internal | 10000/min | Per service | Service-to-service |
## Versioning
### URL Path Versioning (Recommended)
```
/api/v1/users
/api/v2/users
```
**Pros:** Explicit, easy to route, cacheable
**Cons:** URL changes between versions
### Header Versioning
```
GET /api/users
Accept: application/vnd.myapp.v2+json
```
**Pros:** Clean URLs
**Cons:** Harder to test, easy to forget
### Versioning Strategy
```
1. Start with /api/v1/ — don't version until you need to
2. Maintain at most 2 active versions (current + previous)
3. Deprecation timeline:
- Announce deprecation (6 months notice for public APIs)
- Add Sunset header: Sunset: Sat, 01 Jan 2026 00:00:00 GMT
- Return 410 Gone after sunset date
4. Non-breaking changes don't need a new version:
- Adding new fields to responses
- Adding new optional query parameters
- Adding new endpoints
5. Breaking changes require a new version:
- Removing or renaming fields
- Changing field types
- Changing URL structure
- Changing authentication method
```
## Implementation Patterns
### TypeScript (Next.js API Route)
```typescript
import { z } from "zod";
import { NextRequest, NextResponse } from "next/server";
const createUserSchema = z.object({
email: z.string().email(),
name: z.string().min(1).max(100),
});
export async function POST(req: NextRequest) {
const body = await req.json();
const parsed = createUserSchema.safeParse(body);
if (!parsed.success) {
return NextResponse.json({
error: {
code: "validation_error",
message: "Request validation failed",
details: parsed.error.issues.map(i => ({
field: i.path.join("."),
message: i.message,
code: i.code,
})),
},
}, { status: 422 });
}
const user = await createUser(parsed.data);
return NextResponse.json(
{ data: user },
{
status: 201,
headers: { Location: `/api/v1/users/${user.id}` },
},
);
}
```
### Python (Django REST Framework)
```python
from rest_framework import serializers, viewsets, status
from rest_framework.response import Response
class CreateUserSerializer(serializers.Serializer):
email = serializers.EmailField()
name = serializers.CharField(max_length=100)
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ["id", "email", "name", "created_at"]
class UserViewSet(viewsets.ModelViewSet):
serializer_class = UserSerializer
permission_classes = [IsAuthenticated]
def get_serializer_class(self):
if self.action == "create":
return CreateUserSerializer
return UserSerializer
def create(self, request):
serializer = CreateUserSerializer(data=request.data)
serializer.is_valid(raise_exception=True)
user = UserService.create(**serializer.validated_data)
return Response(
{"data": UserSerializer(user).data},
status=status.HTTP_201_CREATED,
headers={"Location": f"/api/v1/users/{user.id}"},
)
```
### Go (net/http)
```go
func (h *UserHandler) CreateUser(w http.ResponseWriter, r *http.Request) {
var req CreateUserRequest
if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
writeError(w, http.StatusBadRequest, "invalid_json", "Invalid request body")
return
}
if err := req.Validate(); err != nil {
writeError(w, http.StatusUnprocessableEntity, "validation_error", err.Error())
return
}
user, err := h.service.Create(r.Context(), req)
if err != nil {
switch {
case errors.Is(err, domain.ErrEmailTaken):
writeError(w, http.StatusConflict, "email_taken", "Email already registered")
default:
writeError(w, http.StatusInternalServerError, "internal_error", "Internal error")
}
return
}
w.Header().Set("Location", fmt.Sprintf("/api/v1/users/%s", user.ID))
writeJSON(w, http.StatusCreated, map[string]any{"data": user})
}
```
## API Design Checklist
Before shipping a new endpoint:
- [ ] Resource URL follows naming conventions (plural, kebab-case, no verbs)
- [ ] Correct HTTP method used (GET for reads, POST for creates, etc.)
- [ ] Appropriate status codes returned (not 200 for everything)
- [ ] Input validated with schema (Zod, Pydantic, Bean Validation)
- [ ] Error responses follow standard format with codes and messages
- [ ] Pagination implemented for list endpoints (cursor or offset)
- [ ] Authentication required (or explicitly marked as public)
- [ ] Authorization checked (user can only access their own resources)
- [ ] Rate limiting configured
- [ ] Response does not leak internal details (stack traces, SQL errors)
- [ ] Consistent naming with existing endpoints (camelCase vs snake_case)
- [ ] Documented (OpenAPI/Swagger spec updated)
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