Custom API Development

Custom REST API design and development following established conventions — resource-oriented URLs, correct HTTP methods, status codes, pagination, filtering and sorting. Built for the use cases of the specific consumers: mobile apps, third-party integrations, partner access and internal microservices.

• Resource-oriented URL structure: /resources, /resources/{id}
• Correct HTTP methods: GET, POST, PUT, PATCH, DELETE
• Consistent response format: envelope, status, data, error
• Pagination: cursor or offset-based with sensible defaults
• Filtering and sorting parameters on collection endpoints
• HTTP status code usage: 200, 201, 204, 400, 401, 403, 404, 422, 500
• Request validation with descriptive error messages
• CORS configuration for browser-based clients

GraphQL API development for use cases where clients need flexibility in what data they request — mobile apps that need different data shapes than the web app, or partner systems that query the data in complex, relationship-traversing ways that REST endpoints don't serve well.

• GraphQL schema design: types, queries, mutations, subscriptions
• Resolver implementation with efficient data loading
• N+1 problem prevention with DataLoader batching
• Query depth and complexity limits to prevent abuse
• Schema documentation with descriptions on all types and fields
• Subscription support for real-time data push
• File upload handling via multipart form
• GraphQL Playground or GraphiQL explorer endpoint

API authentication implementation appropriate to the use case — API keys for server-to-server integrations, OAuth2 with refresh tokens for user-authorised access, JWT for stateless authentication and mTLS for high-security B2B integrations.

• API key authentication with scope assignment
• OAuth2 authorisation code flow for user-delegated access
• JWT generation, validation and refresh token handling
• HTTPS enforcement on all API endpoints
• Input validation and injection prevention on all endpoints
• Sensitive data masking in API responses and logs
• OWASP API Security Top 10 compliance review
• Penetration test preparation and remediation

API versioning strategy and OpenAPI documentation that makes the API easy to consume and maintainable over time — versioned endpoints that allow breaking changes without disrupting existing consumers, and interactive documentation that developers can use to understand and test the API.

• URL-based versioning: /api/v1, /api/v2
• Backwards compatibility commitment per minor version
• Breaking change notification and migration guide
• OpenAPI 3.0 specification maintained alongside code
• Swagger UI or Redoc interactive documentation
• Code examples in multiple languages per endpoint
• Changelog documenting all API changes per version
• Deprecation notice and sunset date for retired versions

API rate limiting and access control to protect the service from abuse and ensure fair usage — per-client rate limits, plan-based quotas, graceful throttling responses and access control that ensures each API key can only access the data it is authorised for.

• Per-API-key rate limits: requests per minute and per hour
• Plan-based quota: different limits per consumer tier
• 429 response with Retry-After header on limit exceeded
• Rate limit headers in responses: limit, remaining, reset
• IP-level rate limiting for unauthenticated endpoints
• Resource-level access control: key can only access own data
• Burst allowance: short spikes above average rate permitted
• Rate limit monitoring and usage analytics per key

Outbound webhook system for pushing events to subscriber systems — when something happens in the platform, the relevant consumer is notified immediately without polling. With signed payloads for security, retry logic for reliability and a delivery log for debugging.

• Event catalogue: defined webhook event types and their payloads
• Consumer webhook registration with endpoint URL and secret
• HMAC-SHA256 payload signature for delivery verification
• Delivery with retry on failure: 3 attempts over 24 hours
• Dead letter queue for permanently failed deliveries
• Webhook delivery log: timestamp, response code, payload
• Manual retry capability from admin dashboard
• Consumer webhook testing tool: send test event to their endpoint