Senior Java Backend Developer (Node.js / TypeScript)

Position: Senior Java Backend Developer (Node.js / TypeScript)
Location: Hybrid (Warsaw, Poland, 1-2 days/week onsite)
Salary: 120-150 PLN/h
Start: 2 weeks
Contract: B2B / Long-term cooperation

Join a team delivering cutting-edge digital solutions at scale. We are partnering with a global leader in telecommunications and digital commerce to grow their Digital Domain team and are currently looking for an experienced Senior Backend Developer with strong Java expertise. In this role, you will contribute to the development of mission-critical BFF (Backend for Frontend) services supporting checkout flows, customer management, and commerce operations used by millions of users worldwide. This is an excellent opportunity for senior engineers who enjoy building scalable backend architectures, designing robust APIs, and working in complex distributed environments.

You will collaborate closely with architects, frontend developers, product teams, and technical leads while helping drive the ongoing transformation toward a modern Node.js / TypeScript ecosystem.

Responsibilities:

• Design, develop, and maintain scalable backend services using Java 21 and Spring Boot 3.x
• Build and integrate REST APIs and support integrations with multiple internal and external systems
• Work with event-driven and distributed architectures, including asynchronous communication and messaging systems
• Support production environments through monitoring, troubleshooting, observability, and continuous improvement activities
• Collaborate with architects, frontend developers, product teams, and technical leads in agile delivery teams
• Participate in technology transformation initiatives toward Node.js / TypeScript ecosystem
• Write unit and integration tests while ensuring high code quality and resilience standards
• Contribute to production-grade engineering practices, reliability, and maintainability of services

Requirements:

• Commercial backend development experience: Senior: 6 years
• Strong expertise in:
  • Java 21
  • Spring Boot 3.x
  • REST API / OpenAPI
  • Spring Security / OAuth2 / JWT
     
• Experience with:
  • API design and system integrations
  • Event-driven architecture and distributed systems
  • Asynchronous flows and messaging concepts
  • Unit and integration testing
  • Monitoring, logging, troubleshooting, and observability
     
• Hands-on knowledge of:
  • MongoDB or similar NoSQL databases
  • Maven or similar build tools
  • Production-grade backend engineering practices
     
• English level: B2 for technical documentation and collaboration
• Senior-level candidates should additionally demonstrate:
  • Distributed system design experience
  • Production ownership and incident resolution
  • Mentoring and technical leadership experience
  • Technology migration/transformation experience
  • Ability to influence engineering standards and best practices

Nice to have:

• Commercial experience with Node.js and TypeScript
• Experience with Express, Fastify, or NestJS frameworks
• Knowledge of Kafka or RabbitMQ
• Experience with Docker and Kubernetes
• Familiarity with GraphQL
• Experience with Terraform and Infrastructure as Code
• Knowledge of OpenTelemetry and distributed tracing
• Experience with Jest or Vitest testing frameworks
• Understanding of npm / pnpm ecosystem

Team structure: Squad within Digital Domain (6-12 developers)

Preferred mindset and personality traits:

• Production Engineer
• Complexity Navigator
• Pragmatic Modernizer
• Status-Quo Challenger