Zensar Technologies

Discussion

Backend API Engineer

Experience Requirements

  • 8+ years of overall experience building and operating backend APIs in production environments

  • Minimum 4 years of hands-on experience with FastAPI specifically (not just general Python API frameworks)

  • Demonstrated experience owning services end-to-end — design, development, deployment, and monitoring

  • Prior experience mentoring engineers or leading technical design discussions is a plus

  • Design and develop high-performance RESTful APIs using FastAPI with clean, validated schemas via Pydantic

  • Architect scalable backend systems, making sound trade-offs on performance, reliability, and maintainability

  • Implement multi-layer caching (Redis + in-memory L1 cache) to optimize latency and throughput

  • Build secure authentication/authorization flows using JWT and OAuth2

  • Integrate with external and internal services using async HTTP clients (HTTPX)

  • Design and consume message queues for asynchronous and event-driven processing

  • Implement standardized, consistent error handling following RFC 9457

  • Write efficient, optimized SQL queries and review database interaction patterns

  • Drive system design discussions and review architecture proposals across teams

  • Write unit/integration tests and uphold high code quality and observability standards

Required Skills (Mandatory)

  • FastAPI

    4+ years of deep, hands-on production experience — routing, dependency injection, async endpoints, middleware, background tasks

  • Pydantic

    Strong command of data validation, serialization, custom validators, and schema design (v1/v2)

  • Redis

    Caching strategies, pub/sub, session/token storage, expiry and eviction policies

Core Skills (Working Knowledge Expected)

  • System Design — ability to architect scalable, fault-tolerant, high-throughput backend systems

  • Authentication & Authorization — OAuth2, RBAC, secure API access patterns

  • JWT — token issuance, validation, refresh flows, and security best practices

  • HTTPX — async HTTP client usage for reliable service-to-service communication

  • API Design — RESTful principles, versioning, rate limiting, backward compatibility

  • Message Queues — experience with Kafka, RabbitMQ, SQS, or Celery for async processing

  • L1 Cache Handling — in-memory/application-level caching alongside Redis (L2) for low-latency reads

  • Exception Handling (RFC 9457) — standardized "Problem Details for HTTP APIs" error responses

  • SQL — strong working knowledge of relational databases (PostgreSQL/MySQL), query optimization, and ORM usage (SQLAlchemy)

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