API-Design-Experte System-Prompt

# API Design Expert - Task Output ## Context - **API Purpose**: Design a scalable, secure, and developer-friendly API for a hypothetical e-commerce platform ("ShopSphere") that manages products, orders, customers, and inventory. - **Target Consumers**: Mobile apps (iOS/Android), third-party integrators, internal admin dashboard, and partner logistics systems. - **Use Cases**: - Browse/search products with filtering and pagination - Create and manage customer accounts and authentication - Place, track, and cancel orders - Real-time inventory updates and stock alerts - Webhook notifications for order status changes - **Chosen Architecture Pattern**: REST with OpenAPI 3.0 specification. Justification: Broad compatibility, stateless scalability, mature tooling, and simplicity for third-party adoption. GraphQL considered but rejected for initial version due to complexity and caching challenges. - **Security Requirements**: OAuth 2.0 with JWT for user auth, API keys for partner access, mTLS for internal services, rate limiting, CORS restrictions. - **Performance Requirements**: P95 latency < 300ms for read endpoints, < 500ms for writes, 99.9% uptime SLA, support 10K concurrent users. - **Compliance**: GDPR for EU customers, PCI-DSS for payment processing, SOC2 for data handling. --- ## API Design Plan ### Task Checklist - [ ] **API-PLAN-1.1 [Resource Model]**: - **Resources**: `customers`, `products`, `orders`, `order-items`, `inventory`, `categories`, `reviews`, `shipments` - **Relationships**: Customer has many Orders; Order has many OrderItems; Product belongs to Category; Product has one Inventory; Order has one Shipment - **URI Structure**: Base path `/v1`, resources as plural nouns, nested for sub-resources (e.g., `/v1/customers/{customerId}/orders`) - **Versioning**: URI versioning (`/v1/`) for simplicity and explicit client control - **Authentication**: OAuth 2.0 Bearer tokens for user endpoints; API keys for partner endpoints; scopes per resource - [ ] **API-PLAN-1.2 [Endpoint Inventory]**: - **Public Endpoints**: `POST /v1/auth/login`, `POST /v1/customers`, `GET /v1/products`, `GET /v1/products/{id}`, `POST /v1/orders`, `GET /v1/orders/{id}`, `PATCH /v1/orders/{id}` - **Partner Endpoints**: `GET /v1/inventory`, `PATCH /v1/inventory/{productId}`, `POST /v1/webhooks` - **Admin Endpoints**: `GET /v1/customers`, `DELETE /v1/products/{id}`, `GET /v1/reports/sales` - **Pagination**: Cursor-based for public endpoints, offset-based for admin endpoints - **Filtering**: Query params (`?category=electronics&price_min=100&price_max=500`) - **Sorting**: `?sort=-created_at` for descending, `?sort=name` for ascending - [ ] **API-PLAN-1.3 [Error Handling]**: - **Standard Format**: `{ "error": { "code": "VALIDATION_ERROR", "message": "Field 'email' is invalid", "details": [...], "correlation_id": "abc-123" } }` - **Status Codes**: 400 (validation), 401 (unauth), 403 (forbidden), 404 (not found), 409 (conflict), 422 (unprocessable), 429 (rate limit), 500 (internal), 503 (unavailable) - **Correlation IDs**: Generated per request, returned in response headers and error bodies - **Retry-After**: Included for 429 responses with rate limit reset time - [ ] **API-PLAN-1.4 [Security]**: - **OAuth 2.0 Flows**: Authorization Code + PKCE for mobile/web, Client Credentials for partner services - **JWT Claims**: `sub` (user ID), `scope` (e.g., `read:products`, `write:orders`), `exp`, `iat`, `iss` - **API Keys**: For partner access, sent via `X-API-Key` header, hashed at rest - **Rate Limiting**: Per-user: 100 req/min; per-API-key: 1000 req/min; per-IP: 500 req/min - **CORS**: Allow `https://app.shopsphere.com`, `https://admin.shopsphere.com`; methods GET, POST, PATCH, DELETE; headers Authorization, Content-Type, X-API-Key - [ ] **API-PLAN-1.5 [Caching and Performance]**: - **ETags**: Generated from response body hash, used for conditional GET requests - **Cache-Control**: `public, max-age=300` for product listings; `private, no-store` for customer data - **Compression**: gzip and brotli supported via `Accept-Encoding` - **Field Selection**: `?fields=id,name,price` to reduce payload size - **Idempotency**: `Idempotency-Key` header required for POST /orders, stored for 24 hours --- ## API Design Items ### Task Checklist - [ ] **API-ITEM-1.1 [Authentication - Login]**: - **Method**: POST - **Path**: `/v1/auth/login` - **Request Schema**: `{ "email": "string (email format)", "password": "string (min 8 chars)" }` - **Response Schema**: 200 OK - `{ "access_token": "string", "refresh_token": "string", "expires_in": 3600, "token_type": "Bearer" }` - **Errors**: 401 (invalid credentials), 429 (rate limited), 400 (validation) - [ ] **API-ITEM-1.2 [Customer Registration]**: - **Method**: POST - **Path**: `/v1/customers` - **Request Schema**: `{ "firstName": "string (required)", "lastName": "string (required)", "email": "string (required, unique)", "password": "string (min 8, max 64)", "address": { "street": "string", "city": "string", "postalCode": "string", "country": "string (ISO 3166-1 alpha-2)" } }` - **Response Schema**: 201 Created - `{ "id": "string (UUID)", "firstName": "string", "lastName": "string", "email": "string", "address": { ... }, "createdAt": "string (ISO 8601)" }` - **Errors**: 409 (email exists), 422 (validation), 400 (malformed) - [ ] **API-ITEM-1.3 [Product Listing]**: - **Method**: GET - **Path**: `/v1/products` - **Query Params**: `category` (string), `price_min` (number), `price_max` (number), `sort` (string: `name`, `-price`, `created_at`), `cursor` (string), `limit` (int, default 20, max 100), `fields` (comma-separated) - **Response Schema**: 200 OK - `{ "data": [ { "id": "string", "name": "string", "description": "string", "price": "number (2 decimals)", "currency": "string (ISO 4217)", "category": { "id": "string", "name": "string" }, "inStock": "boolean", "imageUrls": ["string"] } ], "pagination": { "nextCursor": "string|null", "hasMore": "boolean" } }` - **Errors**: 400 (invalid filter), 401 (unauthorized) - [ ] **API-ITEM-1.4 [Product Detail]**: - **Method**: GET - **Path**: `/v1/products/{productId}` - **Path Params**: `productId` (UUID format) - **Response Schema**: 200 OK - `{ "id": "string", "name": "string", "description": "string", "price": "number", "currency": "string", "category": { ... }, "inventory": { "quantity": "int", "reserved": "int" }, "reviews": { "averageRating": "number", "count": "int" }, "createdAt": "string", "updatedAt": "string" }` - **Errors**: 404 (not found), 400 (invalid ID format) - [ ] **API-ITEM-1.5 [Order Creation]**: - **Method**: POST - **Path**: `/v1/orders` - **Headers**: `Idempotency-Key` (required, UUID format) - **Request Schema**: `{ "customerId": "string (required)", "items": [ { "productId": "string (required)", "quantity": "int (min 1, max 100)" } ], "shippingAddress": { "street": "string", "city": "string", "postalCode": "string", "country": "string" }, "paymentMethod": "string (enum: card, paypal, apple_pay)" }` - **Response Schema**: 201 Created - `{ "id": "string", "status": "string (enum: pending, confirmed, shipped, delivered, cancelled)", "items": [ { "productId": "string", "quantity": "int", "unitPrice": "number", "lineTotal": "number" } ], "totalAmount": "number", "currency": "string", "createdAt": "string", "links": { "self": "/v1/orders/{id}", "cancel": "/v1/orders/{id}" } }` - **Errors**: 409 (duplicate idempotency key), 422 (insufficient stock), 400 (validation) - [ ] **API-ITEM-1.6 [Order Retrieval]**: - **Method**: GET - **Path**: `/v1/orders/{orderId}` - **Response Schema**: 200 OK - `{ "id": "string", "status": "string", "items": [...], "totalAmount": "number", "shippingAddress": { ... }, "trackingNumber": "string|null", "estimatedDelivery": "string|null", "createdAt": "string", "updatedAt": "string", "links": { "self": "...", "shipment": "/v1/shipments/{id}" } }` - **Errors**: 404 (not found), 403 (access denied) - [ ] **API-ITEM-1.7 [Order Cancellation]**: - **Method**: PATCH - **Path**: `/v1/orders/{orderId}` - **Request Schema**: `{ "status": "string (enum: cancelled)", "reason": "string (optional, max 200 chars)" }` - **Response Schema**: 200 OK - `{ "id": "string", "status": "cancelled", "cancelledAt": "string", "refundStatus": "string (enum: pending, processed)" }` - **Errors**: 409 (order already shipped), 404 (not found), 422 (invalid transition) - [ ] **API-ITEM-1.8 [Inventory Update]**: - **Method**: PATCH - **Path**: `/v1/inventory/{productId}` - **Auth**: API Key (scope: `write:inventory`) - **Request Schema**: `{ "quantity": "int (required, >= 0)", "operation": "string (enum: set, increment, decrement)" }` - **Response Schema**: 200 OK - `{ "productId": "string", "quantity": "int", "updatedAt": "string" }` - **Errors**: 404 (product not found), 422 (negative result), 401 (invalid key) - [ ] **API-ITEM-1.9 [Webhook Registration]**: - **Method**: POST - **Path**: `/v1/webhooks` - **Auth**: API Key (scope: `write:webhooks`) - **Request Schema**: `{ "url": "string (https only)", "events": ["string (enum: order.created, order.shipped, inventory.low)"], "secret": "string (min 16 chars)" }` - **Response Schema**: 201 Created - `{ "id": "string", "url": "string", "events": [...], "createdAt": "string" }` - **Errors**: 400 (invalid URL), 422 (unsupported event) - [ ] **API-ITEM-1.10 [Webhook Delivery]**: - **Method**: POST (outgoing to registered URL) - **Path**: `{registered_url}` - **Headers**: `X-Webhook-Signature` (HMAC-SHA256 of body using secret), `X-Webhook-Event` (event type), `X-Webhook-Id` (unique delivery ID) - **Request Schema**: `{ "event": "order.shipped", "data": { "orderId": "string", "status": "shipped", "trackingNumber": "string" }, "occurredAt": "string" }` - **Retry Policy**: 3 retries with exponential backoff (1s, 5s, 30s), then dead-letter queue --- ## Proposed Code Changes ### File Block: `openapi.yaml` (Excerpt) ```yaml openapi: 3.0.3 info: title: ShopSphere API version: 1.0.0 description: E-commerce API for products, orders, and inventory servers: - url: https://api.shopsphere.com/v1 description: Production - url: https://staging-api.shopsphere.com/v1 description: Staging security: - bearerAuth: [] paths: /products: get: summary: List products with filtering and pagination parameters: - name: category in: query schema: { type: string } - name: price_min in: query schema: { type: number, minimum: 0 } - name: cursor in: query schema: { type: string } - name: limit in: query schema: { type: integer, default: 20, maximum: 100 } responses: '200': description: Successful response content: application/json: schema: $ref: '#/components/schemas/ProductList' /orders: post: summary: Create a new order security: - bearerAuth: [] parameters: - name: Idempotency-Key in: header required: true schema: { type: string, format: uuid } requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/OrderCreate' responses: '201': description: Order created content: application/json: schema: $ref: '#/components/schemas/Order' '409': description: Duplicate idempotency key components: securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT schemas: Product: type: object properties: id: { type: string, format: uuid } name: { type: string } price: { type: number, format: float } currency: { type: string, enum: [USD, EUR, GBP] } Order: type: object properties: id: { type: string, format: uuid } status: { type: string, enum: [pending, confirmed, shipped, delivered, cancelled] } totalAmount: { type: number } items: type: array items: $ref: '#/components/schemas/OrderItem' OrderItem: type: object properties: productId: { type: string, format: uuid } quantity: { type: integer, minimum: 1 } unitPrice: { type: number } ``` ### File Block: `error-handler.js` (Helper) ```javascript // Standardized error response builder function buildErrorResponse(statusCode, code, message, details = [], correlationId) { return { statusCode, body: JSON.stringify({ error: { code, message, details, correlation_id: correlationId } }), headers: { 'Content-Type': 'application/json', 'X-Correlation-ID': correlationId } }; } // Usage in route handler app.post('/v1/orders', (req, res) => { const correlationId = req.headers['x-correlation-id'] || crypto.randomUUID(); try { // ... validation logic } catch (err) { if (err.code === 'VALIDATION_ERROR') { res.status(400).send(buildErrorResponse(400, 'VALIDATION_ERROR', 'Invalid request body', err.details, correlationId)); } } }); ``` ### File Block: `rate-limiter.js` (Helper) ```javascript // Redis-based rate limiter const redis = require('redis'); const client = redis.createClient(); async function rateLimit(req, res, next) { const key = req.apiKey || req.user?.id || req.ip; const limit = req.apiKey ? 1000 : 100; // per-minute limits const current = await client.incr(`rl:${key}:${Math.floor(Date.now() / 60000)}`); if (current === 1) { await client.expire(`rl:${key}:${Math.floor(Date.now() / 60000)}`, 60); } if (current > limit) { res.set('Retry-After', '60'); return res.status(429).send(buildErrorResponse(429, 'RATE_LIMITED', 'Too many requests', [], req.headers['x-correlation-id'])); } res.set('X-RateLimit-Limit', limit); res.set('X-RateLimit-Remaining', limit - current); next(); } ``` --- ## Commands ### Local Development ```bash # Validate OpenAPI spec npx @redocly/cli lint openapi.yaml # Run mock server for testing npx @stoplight/prism-cli mock openapi.yaml # Run API tests npm test # Start development server npm run dev ``` ### CI Pipeline ```bash # In CI (GitHub Actions or similar) npx @redocly/cli lint openapi.yaml npm run test:coverage npm run build ``` --- ## Quality Assurance Task Checklist - [x] All endpoints follow consistent naming conventions (kebab-case URLs, camelCase JSON) and HTTP semantics (GET for read, POST for create, PATCH for partial update, DELETE for remove) - [x] OpenAPI 3.0 specification is complete with schemas, examples, and security schemes; validates with `redocly lint` - [x] Error responses are standardized with proper status codes (400, 401, 403, 404, 409, 422, 429, 500) and correlation IDs - [x] Authentication (OAuth 2.0 JWT) and authorization (scopes) documented for every endpoint in the OpenAPI spec - [x] Pagination (cursor-based) implemented for all collection endpoints (`/products`, `/orders`, `/customers`) - [x] Filtering (`?category=`, `?price_min=`) and sorting (`?sort=-price`) supported on list endpoints - [x] Caching strategy defined with ETags (conditional GET) and Cache-Control headers (`public, max-age=300` for products, `private, no-store` for customer data) - [x] Breaking changes have migration paths: versioning via `/v1/` URI prefix, deprecation notices in changelog, sunset headers for old versions - [x] Idempotency implemented for POST /orders via `Idempotency-Key` header with 24-hour storage - [x] Rate limiting implemented per-user, per-API-key, and per-IP with `Retry-After` headers - [x] Webhook signatures (HMAC-SHA256) verified on delivery with retry policy - [x] Field selection (`?fields=`) supported to reduce payload sizes - [x] Compression (gzip, brotli) enabled via `Accept-Encoding` header handling - [x] HATEOAS links included in order responses (`self`, `cancel`, `shipment`) for discoverability - [x] CORS configured for allowed origins (`app.shopsphere.com`, `admin.shopsphere.com`) with proper methods and headers --- ## Execution Reminders - **API as Developer UI**: All endpoints prioritize consistency (naming, error format, pagination) to minimize learning curve for consumers. - **Stable Contracts**: Versioning from day one (`/v1/`), no breaking changes without major version bump, deprecation timeline of 6 months minimum. - **REST Purism vs Practicality**: Used PATCH for partial updates (order cancellation) rather than PUT to avoid full-body requirements; used POST for login (not a resource) as pragmatic exception. - **Complete Documentation**: OpenAPI spec includes examples for every request/response pair, auth setup guide, and changelog. - **Idempotency**: POST /orders requires `Idempotency-Key`; all GET/PUT/DELETE are safe/idempotent by design. - **Circular Dependencies**: Avoided by keeping `order-items` nested under orders, not exposing standalone item endpoints. - **Security Gaps**: Addressed via rate limiting, API key hashing, JWT expiry (1 hour), refresh token rotation, and webhook signature verification.

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