Backend API Engineer

Senior Backend API Engineer with 8+ years of experience building and scaling production APIs, including at least 4 years working hands-on with FastAPI. You will design, build, and maintain high-performance, secure backend services, and act as a technical leader on architecture and system design decisions.

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

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

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.