Api Development Interview Questions

REST (Representational State Transfer) is an architectural style with principles: statelessness, client-server separation, cacheable resources, uniform interface, layered system. Uses HTTP methods (GET, POST, PUT, DELETE) for CRUD operations.

API authentication methods include: JWT tokens, OAuth 2.0, API keys, Basic Auth, Bearer tokens. Implementation involves token generation, validation, middleware for protection, and proper error handling. Consider security best practices like token expiration.

Best practices include: consistent response structure, proper HTTP status codes, clear error messages, pagination metadata, proper content type headers. Use envelope pattern when needed, handle nested resources, implement proper serialization.

Versioning strategies include: URI versioning (v1/api), header versioning (Accept header), query parameter versioning. Consider backward compatibility, deprecation policies, documentation. Choose strategy based on client needs.

Rate limiting controls request frequency. Implementation includes: tracking requests per client, setting time windows, using tokens/keys, implementing cooldown periods. Use Redis/cache for distributed systems. Return proper headers for limit status.

CORS (Cross-Origin Resource Sharing) handled through proper headers: Access-Control-Allow-Origin, Allow-Methods, Allow-Headers. Implementation includes preflight requests handling, proper middleware configuration, security considerations.

Resources/transformers format API responses: converting models to JSON/arrays, handling relationships, hiding sensitive data. Features include conditional attributes, nested resources, custom transformations. Important for consistent response formatting.

API caching strategies include: HTTP cache headers, response caching, query result caching. Use ETags, Cache-Control headers, implement cache invalidation. Consider cache layers (client, CDN, server) and cache lifetime.

GraphQL is query language for APIs. Features: single endpoint, client-specified data, strong typing, real-time with subscriptions. Differs from REST in data fetching, versioning approach, and response structure. Consider use case for implementation.

File upload handling includes: multipart form data, proper validation, secure storage, progress tracking. Consider chunked uploads for large files, implement proper error handling, use secure file operations.

Webhooks are HTTP callbacks for real-time notifications. Implementation includes: endpoint registration, payload signing, retry logic, event queuing. Consider security, validation, and proper error handling.

API documentation tools include: Swagger/OpenAPI, API Blueprint, automated documentation generation. Include: endpoints, parameters, responses, examples. Keep documentation updated, consider interactive documentation.

Common threats include: injection attacks, unauthorized access, MITM attacks, DoS/DDoS, data exposure. Implement: authentication, rate limiting, input validation, proper encryption, secure headers.

API testing includes: unit tests, integration tests, end-to-end tests. Use tools like PHPUnit, Postman, automated testing. Test authentication, validation, error cases, performance. Implement CI/CD pipeline.

Throttling controls API usage by limiting request rate/volume. Implementation includes: token bucket algorithm, sliding window, concurrent request limiting. Consider user tiers, custom limits, proper error responses.

Error handling includes: proper HTTP status codes, consistent error format, detailed messages, error logging. Implement global exception handler, format exceptions properly, consider security in error messages.

OAuth 2.0 is authorization framework. Implementation includes: authorization flows, token management, scope handling, refresh tokens. Consider security best practices, proper flow selection, token storage.

Pagination methods include: offset/limit, cursor-based, page-based. Include metadata (total, next/prev links), handle large datasets, implement proper caching. Consider performance and use case requirements.

JWTs are encoded tokens containing claims. Structure: header, payload, signature. Used for authentication/authorization. Implementation includes token generation, validation, refresh mechanisms. Consider security implications.

Logging/monitoring includes: request/response logging, error tracking, performance metrics, usage analytics. Implement proper log levels, monitoring tools integration, alerting systems. Consider privacy and security.

API gateway provides single entry point for multiple services. Features: request routing, authentication, rate limiting, caching, monitoring. Benefits include centralized control, security, scalability.

Request validation includes: input sanitization, schema validation, type checking, business rule validation. Implement validation middleware, proper error responses, custom validation rules. Consider performance impact.

Microservices are small, independent services. Implementation includes: service communication, data consistency, deployment strategies, service discovery. Consider scalability, monitoring, error handling.

Optimization includes: response caching, query optimization, proper indexing, compression, connection pooling. Consider bottlenecks, monitoring, scaling strategies. Implement proper profiling.

Composition combines multiple API calls into single endpoint. Aggregation combines data from multiple services. Consider performance, error handling, data consistency. Implement proper caching strategies.

Search implementation includes: query parameters, filtering, sorting, full-text search. Consider search engines integration, performance optimization, proper indexing. Implement relevance scoring.

Common patterns include: Repository, Factory, Strategy, Observer, Adapter. Used for code organization, maintainability, scalability. Consider use case requirements, team familiarity, implementation complexity.

Deprecation strategy includes: versioning, notification period, documentation updates, migration guides. Implement warning headers, monitoring deprecated usage, proper communication. Consider client impact.

Orchestration coordinates multiple API calls/services. Includes: workflow management, error handling, rollback mechanisms. Consider transaction management, service dependencies, monitoring. Implement proper logging.

Analytics implementation includes: usage tracking, performance metrics, error rates, user behavior. Consider data collection, storage, visualization tools. Implement proper privacy measures.