Master REST and GraphQL API design principles to build intuitive, scalable, and maintainable APIs that delight developers. Use when designing new APIs, reviewing API specifications, or establishing API design standards.
Master REST and GraphQL API design principles to build intuitive, scalable, and maintainable APIs that delight developers. Use when designing new APIs, reviewing API specifications, or establishing API design standards.
API Design Principles
Master REST and GraphQL API design principles to build intuitive, scalable, and maintainable APIs that delight developers and stand the test of time.
When to Use This Skill
Designing new REST or GraphQL APIs
Refactoring existing APIs for better usability
Establishing API design standards for your team
Reviewing API specifications before implementation
Migrating between API paradigms (REST to GraphQL, etc.)
Creating developer-friendly API documentation
Optimizing APIs for specific use cases (mobile, third-party integrations)
Core Concepts
1. RESTful Design Principles
Resource-Oriented Architecture
Resources are nouns (users, orders, products), not verbs
Use HTTP methods for actions (GET, POST, PUT, PATCH, DELETE)
URLs represent resource hierarchies
Consistent naming conventions
HTTP Methods Semantics:
GET: Retrieve resources (idempotent, safe)
POST: Create new resources
PUT: Replace entire resource (idempotent)
PATCH: Partial resource updates
DELETE: Remove resources (idempotent)
2. GraphQL Design Principles
Schema-First Development
Types define your domain model
Queries for reading data
Mutations for modifying data
Subscriptions for real-time updates
Query Structure:
Clients request exactly what they need
Single endpoint, multiple operations
Strongly typed schema
Introspection built-in
3. API Versioning Strategies
URL Versioning:
/api/v1/users
/api/v2/users
Header Versioning:
Accept: application/vnd.api+json; version=1
Query Parameter Versioning:
/api/users?version=1
REST API Design Patterns
Pattern 1: Resource Collection Design
# Good: Resource-oriented endpoints
GET /api/users # List users (with pagination)
POST /api/users # Create user
GET /api/users/{id} # Get specific user
PUT /api/users/{id} # Replace user
PATCH /api/users/{id} # Update user fields
DELETE /api/users/{id} # Delete user# Nested resources
GET /api/users/{id}/orders # Get user's orders
POST /api/users/{id}/orders # Create order for user# Bad: Action-oriented endpoints (avoid)
POST /api/createUser
POST /api/getUserById
POST /api/deleteUser
# schema.graphql# Clear type definitionstype User {id: ID!email: String!name: String!createdAt: DateTime!# Relationships
orders(first: Int =20after: String
status: OrderStatus
): OrderConnection!profile: UserProfile
}type Order {id: ID!status: OrderStatus!total: Money!items:[OrderItem!]!createdAt: DateTime!# Back-referenceuser: User!}# Pagination pattern (Relay-style)type OrderConnection {edges:[OrderEdge!]!pageInfo: PageInfo!totalCount: Int!}type OrderEdge {node: Order!cursor: String!}type PageInfo {hasNextPage: Boolean!hasPreviousPage: Boolean!startCursor: String
endCursor: String
}# Enums for type safetyenum OrderStatus {
PENDING
CONFIRMED
SHIPPED
DELIVERED
CANCELLED
}# Custom scalarsscalar DateTime
scalar Money
# Query roottypeQuery{
user(id: ID!): User
users(first: Int =20after: String
search: String
): UserConnection!
order(id: ID!): Order
}# Mutation roottypeMutation{
createUser(input: CreateUserInput!): CreateUserPayload!
updateUser(input: UpdateUserInput!): UpdateUserPayload!
deleteUser(id: ID!): DeleteUserPayload!
createOrder(input: CreateOrderInput!): CreateOrderPayload!}# Input types for mutationsinput CreateUserInput {email: String!name: String!password: String!}# Payload types for mutationstype CreateUserPayload {user: User
errors:[Error!]}type Error {field: String
message: String!}
Pattern 2: Resolver Design
from typing importOptional, Listfrom ariadne import QueryType, MutationType, ObjectType
from dataclasses import dataclass
query = QueryType()
mutation = MutationType()
user_type = ObjectType("User")
@query.field("user")asyncdefresolve_user(obj, info, id: str) -> Optional[dict]:
"""Resolve single user by ID."""returnawait fetch_user_by_id(id)
@query.field("users")asyncdefresolve_users(
obj,
info,
first: int = 20,
after: Optional[str] = None,
search: Optional[str] = None) -> dict:
"""Resolve paginated user list."""# Decode cursor
offset = decode_cursor(after) if after else0# Fetch users
users = await fetch_users(
limit=first + 1, # Fetch one extra to check hasNextPage
offset=offset,
search=search
)
# Pagination
has_next = len(users) > first
if has_next:
users = users[:first]
edges = [
{
"node": user,
"cursor": encode_cursor(offset + i)
}
for i, user inenumerate(users)
]
return {
"edges": edges,
"pageInfo": {
"hasNextPage": has_next,
"hasPreviousPage": offset > 0,
"startCursor": edges[0]["cursor"] if edges elseNone,
"endCursor": edges[-1]["cursor"] if edges elseNone
},
"totalCount": await count_users(search=search)
}
@user_type.field("orders")asyncdefresolve_user_orders(user: dict, info, first: int = 20) -> dict:
"""Resolve user's orders (N+1 prevention with DataLoader)."""# Use DataLoader to batch requests
loader = info.context["loaders"]["orders_by_user"]
orders = await loader.load(user["id"])
return paginate_orders(orders, first)
@mutation.field("createUser")asyncdefresolve_create_user(obj, info, input: dict) -> dict:
"""Create new user."""try:
# Validate input
validate_user_input(input)
# Create user
user = await create_user(
email=input["email"],
name=input["name"],
password=hash_password(input["password"])
)
return {
"user": user,
"errors": []
}
except ValidationError as e:
return {
"user": None,
"errors": [{"field": e.field, "message": e.message}]
}
Pattern 3: DataLoader (N+1 Problem Prevention)
from aiodataloader import DataLoader
from typing importList, OptionalclassUserLoader(DataLoader):
"""Batch load users by ID."""asyncdefbatch_load_fn(self, user_ids: List[str]) -> List[Optional[dict]]:
"""Load multiple users in single query."""
users = await fetch_users_by_ids(user_ids)
# Map results back to input order
user_map = {user["id"]: user for user in users}
return [user_map.get(user_id) for user_id in user_ids]
classOrdersByUserLoader(DataLoader):
"""Batch load orders by user ID."""asyncdefbatch_load_fn(self, user_ids: List[str]) -> List[List[dict]]:
"""Load orders for multiple users in single query."""
orders = await fetch_orders_by_user_ids(user_ids)
# Group orders by user_id
orders_by_user = {}
for order in orders:
user_id = order["user_id"]
if user_id notin orders_by_user:
orders_by_user[user_id] = []
orders_by_user[user_id].append(order)
# Return in input orderreturn [orders_by_user.get(user_id, []) for user_id in user_ids]
# Context setupdefcreate_context():
return {
"loaders": {
"user": UserLoader(),
"orders_by_user": OrdersByUserLoader()
}
}
Best Practices
REST APIs
Consistent Naming: Use plural nouns for collections (/users, not /user)
Stateless: Each request contains all necessary information
Use HTTP Status Codes Correctly: 2xx success, 4xx client errors, 5xx server errors
Version Your API: Plan for breaking changes from day one
Pagination: Always paginate large collections
Rate Limiting: Protect your API with rate limits
Documentation: Use OpenAPI/Swagger for interactive docs
GraphQL APIs
Schema First: Design schema before writing resolvers
Avoid N+1: Use DataLoaders for efficient data fetching
Input Validation: Validate at schema and resolver levels
Error Handling: Return structured errors in mutation payloads
Pagination: Use cursor-based pagination (Relay spec)
Deprecation: Use @deprecated directive for gradual migration
Monitoring: Track query complexity and execution time
Common Pitfalls
Over-fetching/Under-fetching (REST): Fixed in GraphQL but requires DataLoaders
Breaking Changes: Version APIs or use deprecation strategies