API GraphQL moderne avec federation, DataLoader, optimisations.
GraphQL vs REST
GraphQL — 1 query sur-mesure, no versioning, introspection auto
REST — Multiple endpoints, over-fetching, v1/v2/v3
Apollo Federation
# Users service
type User @key(fields: "id") { id: ID!, name: String! }
extend type User @key(fields: "id") { id: ID! @external orders: [Order!]! }
Gateway compose automatiquement les services.
## N+1 Problem — DataLoader
```javascript
// ❌ N+1 queries
User: { orders: (u) => db.orders.findByUserId(u.id) }
// ✅ DataLoader batch
const loader = new DataLoader(async (ids) => {
const orders = await db.orders.findByUserIds(ids);
return ids.map(id => orders.filter(o => o.userId === id));
});
User: { orders: (u) => loader.load(u.id) }
Patterns
Pagination (Relay)
type UserConnection {
edges: [{ node: User!, cursor: String! }]!
pageInfo: { hasNextPage: Boolean!, endCursor: String }!
}
Error Handling
type CreateUserPayload {
user: User
errors: [{ field: String, message: String! }]
}
Optimizations
DataLoader — Batch + cache
Persisted Queries — Hash lookup
Depth Limiting — Anti-DoS
Cost Analysis — Query budget
Voir @api-designer pour design