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

At Zensar, we're "experience-led everything". We are committed to conceptualizing, designing, engineering, marketing, and managing digital solutions and experiences for over 130 leading enterprises. We are a company driven by a bold purpose: Together, we shape experiences for better futures. Whether for our clients, our people, or the world around us, this belief powers everything we do. At the heart of our culture is ONE with Client - a set of four core values that reflect who we are and how we work: One Zensar, Nurturing, Empowering, and Client Focus.

Part of the $4.8 billion RPG Group, we're a community of 10,000+ innovators across 30+ global locations, including Milpitas, Seattle, Princeton, Cape Town, London, Zurich, Singapore, and Mexico City. Explore Life at Zensar and join us to Grow. Own. Achieve. Learn. to be the best version of yourself.

We believe the best work happens when individuality is celebrated, growth is encouraged, and well-being is prioritized. We are an equal employment opportunity (EEO) and affirmative action employer, committed to creating an inclusive workplace. All qualified applicants will be considered without regard to race, creed, color, ancestry, religion, sex, national origin, citizenship, age, sexual orientation, gender identity, disability, marital status, family medical leave status, or protected veteran status.

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)

• 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