Senior Java Backend Engineer

About the role

NTT Data Greece is looking for a motivated and experienced Senior Java Backend Engineer in Athens to support the European Commission on the DPP project. You will develop backend features from detailed specifications and work in an international delivery environment.

Key responsibilities

• Develop backend application features from detailed functional and architecture specifications.
• Design and implement API-first backend services and REST APIs aligned with agreed OpenAPI contracts.
• Translate high-level architecture specs into detailed technical designs and implementation plans.
• Contribute to backend architecture decisions, ensuring separation of concerns, bounded contexts, maintainability, scalability and operational simplicity.
• Produce quality code including unit and integration testing, contract validation and architectural governance checks.
• Support CI/CD-driven delivery, trunk-based development and reliable release practices.
• Collaborate with architects, business analysts, UX designers, QA, DevOps and frontend teams.

Required profile

• Over 7 years of previous experience with Java and Spring Boot backend projects.
• Strong knowledge of modern Java practices (immutability, records, Optional, Streams API, constructor-based DI, clean service/repository layering).
• Experience with Spring WebFlux or reactive programming for I/O-bound, asynchronous, high-concurrency or event-driven processing.
• Experience with MapStruct or equivalent mappers and strong Spring Security knowledge (OAuth2 / OpenID Connect, JWT, authorization rules, method-level security).
• RESTful API experience with OpenAPI, JSON/XML/XSD, AsyncAPI, and third-party integrations.
• Hands-on MongoDB experience (data modelling, indexing, query optimisation, migrations, transactional outbox, idempotent consumers).
• JUnit 5, Mockito / Spring MockBean and integration testing with Testcontainers; familiarity with tools like Spectral, Schemathesis, Microcks, ArchUnit is valuable.
• Docker, Kubernetes, Helm, CI/CD pipelines, Linux, Git and Maven.
• English B2 or higher; experience in international projects is highly valued.

What we offer

• Health insurance for the employee and one dependent family member (fully paid by NTT DATA).
• Meal vouchers of 120 EUR per month (12 months).
• Corporate mobile phone and teleworking equipment allowance.
• Internal training platform account and access to Open Up mental health service.
• 26 days of paid annual leave plus two fixed days (Good Friday and Whit Monday).
• BeFlex work-life balance policy, structured training, annual reviews and a mentorship program.