Hire a Certified
Back-End Developer
in Days, Not Months

How do you design a scalable REST API, and what decisions do you make around versioning, error handling, and authentication?

Strong candidates discuss resource-based URL design, consistent error response formats, JWT vs. OAuth tradeoffs, and versioning strategies (URI vs. header). Look for awareness of rate limiting, idempotency for write operations, and pagination patterns — not just "I've built APIs before."

How do you optimize a database-heavy application that is experiencing performance issues?

Look for a systematic diagnostic approach: query analysis with EXPLAIN, index evaluation, N+1 query detection, connection pooling, caching strategies (Redis, CDN), and read replica configuration. Developers who jump straight to "add an index" without diagnosing the actual bottleneck signal limited production experience.

Describe your approach to securing a back-end application. What are the most common vulnerabilities you protect against?

Mature back-end developers reference OWASP Top 10 — SQL injection, XSS, CSRF, broken authentication, insecure deserialization — and describe specific mitigation patterns: parameterized queries, input validation, secrets management, and least-privilege service accounts. Security awareness should be built into development, not bolted on at the end.

How have you approached designing or working within a microservices architecture? What challenges did you encounter?

Look for hands-on experience with service decomposition, inter-service communication (REST vs. gRPC vs. message queues), distributed tracing, and failure handling (circuit breakers, retries). Developers who have only worked in monoliths may struggle with the operational complexity of microservices in production.

How do you handle asynchronous processing and background jobs in your applications?

Strong candidates describe task queues (Celery, Sidekiq, Bull), message brokers (RabbitMQ, Kafka, SQS), idempotency in job execution, dead letter queues for failure handling, and monitoring for queue depth. Candidates who have never thought about job failure modes or retry logic signal limited production systems exposure.

Walk me through how you collaborate with front-end developers and DevOps teams during a feature build.

Top back-end developers describe API contract definition before implementation (OpenAPI/Swagger), mock server setup for parallel front-end development, environment parity with DevOps, and deployment coordination. Candidates who only hand off a finished API without cross-functional alignment create integration friction and release risk.