Integration Developer (Node.js, TypeScript on AWS)

Job Description
We are seeking an Integration Developer to build a containerised gateway service on AWS, using Node.js, TypeScript and Fastify on ECS Fargate. The service routes all transactional email from commerce and order management systems to a new email service provider. The developer will build:
a pass-through API
a backward-compatible API that converts legacy requests and responses using configurable mappings, so new campaigns can be added without a code release
The role covers idempotent processing, retry and failure handling, audit logging, event publishing and tracing, with security, resilience and observability built into the application. Development is OpenAPI-first, uses AI-assisted coding tools and is checked with contract tests built from real traffic. The developer will work closely with the architect, DevOps and QA on a fast build.
Responsibilities
Develop REST APIs in Node.js/TypeScript (Fastify or similar) to OpenAPI specifications, with request validation and structured error handling.
Implement legacy auth/token emulation and request/response transformation for the backward-compatible API, without requiring consumer payload changes.
Build configuration-driven campaign, field and error-code mappings using AWS AppConfig, supporting publisher and regional variants.
Integrate securely with third-party email provider APIs using Secrets Manager credentials; implement safe error handling and PII-aware structured logging.
Build idempotency with DynamoDB conditional writes, bounded timeouts, retry/backoff, circuit breaker and SQS/DLQ recovery, without changing the agreed API contract.
Write audit records, publish events to EventBridge and propagate correlation IDs for end-to-end tracing.
Use approved AI coding assistants to build mapping code, API specifications, unit tests and contract tests from sanitised discovery artefacts; review and correct every generated change.
Support SIT, UAT, cutover and post-release stabilisation, including defect fixes and tuning.
Qualifications
Required Skills & Competencies
Strong hands-on Node.js and TypeScript backend development, including Fastify (or a similar framework), asynchronous programming, REST/JSON APIs, validation and structured error handling.
Working experience with AWS SDK integrations: DynamoDB, Secrets Manager, SQS/DLQ, and containerised deployment to ECS Fargate.
Practical AI-assisted application development using an approved coding assistant: supplying contract context, iterating on generated code and verifying correctness with tests.
API integration and transformation, legacy contract compatibility, token-based authentication and configuration-driven business mappings.
Unit, API and contract-test development; Git-based peer review, CI/CD integration and production debugging using logs and distributed traces.
Idempotency, retry safety, timeout handling, circuit breakers and secure handling of credentials and personal data.
Good-to-Have
AWS AppConfig, EventBridge, OpenTelemetry/ADOT, CloudWatch and X-Ray
Jest or an equivalent TypeScript testing framework; Docker
Java / Spring Boot exposure
Qualifications
5–8 years of relevant software development experience, including hands-on backend/API integration delivery.
B.E./B.Tech/MCA or equivalent
About Us
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.

Skills
JavaScript, TypeScript, Node.js, AWS, Java, Spring Boot, Spring, REST API, Git, Docker

Work arrangement
No