Overseas Contractor- Senior Java Backend Developer

LTM; Gdynia; Hybrid; PLN 260,000 - 360,000; Full time

Job summary

LTM is seeking a Senior Java Backend Developer with payments experience to design and build secure, high-performance payment services. You will work with Core Java, Spring Boot microservices, and Kafka, applying AI-assisted engineering to deliver high-quality software.

You will collaborate with Nordic client stakeholders, owning solutions from specification through production, in a hybrid setup in Poland. Responsibilities include designing payment microservices, implementing event-driven flows,

Qualifications

• 10 years in Java backend development with 5 years in payments or banking.
• Expert in Core Java and Spring Boot microservices.
• Experience with Kafka and event-driven architectures.
• Hands-on with OpenAPI/Swagger and API design.
• Knowledge of security, resilience, and data protection in banking systems.

Responsibilities

• Design and build scalable payment microservices (initiation, clearing, settlement).
• Implement event-driven flows with Kafka, including idempotency and reliable retry.
• Draft specifications, API contracts, and data models for AI-assisted development.
• Lead and mentor peers in modern Java and AI-assisted engineering practices.
• Support production and diagnose incidents in payment systems.

Skills

Java

Spring Boot

Microservices

Kafka

SQL/Databases

Sys/DevOps

Tools

Docker

Kubernetes

OpenShift

GitHub Actions

Maven

Jenkins

Nexus/Artifactory

Job description

Role Description

Role- Senior Java Backend Developer- Payments AI Enabled Spec Driven Development

Role Details

Location: Gdynia and Warsaw, Poland - hybrid client site

Hiring: B2B/ Subcon

Experience: 10 years in Java backend development including 5 years in payments or banking

Role Summary

We are looking for a senior Java backend developer with hands on payments experience to design and build secure high performance payment services. The candidate should be expert in Core Java Spring Boot microservices and Kafka. They should also use AI assisted engineering especially spec driven development to deliver high-quality software faster. Working directly with Nordic client stakeholders they will own solutions from specification through to production.

Key Responsibilities

• Design, develop and maintain scalable payment microservices for payment initiation, clearing, settlement and reconciliation.
• Build event-driven high throughput flows using Kafka with idempotency, exactly-once handling and reliable retry and error handling.
• Write clear specifications, requirements, acceptance criteria, API contracts, data models and use them as the single source of truth for AI assisted design, code generation and testing.
• Use AI coding assistants and agents e.g. GitHub Copilot Spec Kit or similar to turn specifications into plans, tasks, code and tests. Critically review all AI-generated output for correctness, security and compliance.
• Design REST APIs contract-first using OpenAPI and keep specifications and code in sync.
• Make sure solutions meet banking-grade standards for security, resilience, audit and data protection.
• Work with product owners, architects and testers in Agile SAFe teams.
• Mentor other developers on modern Java and AI assisted engineering practices.
• Support production and analyse incidents for business-critical payment systems.

Required Skills

Java and backend

• Expert in Java 17, Java 21 (preferred), Spring Boot 3, Spring Framework, Spring Data, Hibernate JPA.
• Spring Security with OAuth2/OIDC, JWT and mTLS.
• Microservices patterns: API gateway, circuit breaker, saga, outbox, CQRS, and event sourcing.
• Kafka producers, consumers, partitioning, schema registry, Kafka Streams.
• Contract-first REST API development with OpenAPI/Swagger, API versioning and documentation.

Payments domain

• Hands-on experience with ISO 20022 messages pain, pacs, camt and SWIFT MT/MX migration.
• Knowledge of SEPA Credit Transfer, SEPA Instant SCT Inst, SEPA Direct Debit and real-time payment schemes such as TIPS, RT1.
• Understanding of the payment lifecycle: initiation, validation, screening, routing, clearing, settlement and reconciliation.
• Awareness of EU regulation including PSD2/Open Banking APIs, the EU Instant Payments Regulation, DORA, GDPR and AML sanctions screening.

AI and spec-driven development

• Practical experience with spec-driven development, writing structured testable specifications that drive AI-generated design, code and tests.
• Skilled use of AI coding assistants and agents in daily development, prompt and context engineering, iterating on output, generating tests.
• Ability to validate AI-generated code for quality, security and performance and to apply guardrails such as code review, static analysis and policy checks.
• Understanding of responsible AI in regulated environments, no sensitive data in prompts, traceability, human oversight.

Data and databases

• Strong relational database skills: Oracle, MS SQL, PostgreSQL; complex queries, performance tuning, transactions and locking.
• Database migration tools: Flyway, Liquibase.

DevOps and quality

• Docker and Kubernetes, OpenShift (a plus).
• CICD: Git, Maven, Bamboo, Jenkins, GitHub Actions, Ansible, artifact repositories Nexus, Artifactory.
• Testing: JUnit 5, Mockito, Testcontainers, contract testing (Pact, Spring Cloud Contract), performance testing.
• Code quality and security: SonarQube, static and dependency security scanning, SAST, SCa, OWASP Top 10.
• Shell scripting and scheduling tools: UC4, Automic, AutoSys, ControlM.

Ways of working

• Experience in Agile and SAFe delivery.

Good to Have

• Cloud platforms: Azure, AWS, GCP.
• Observability: Grafana, Prometheus, OpenTelemetry, AppDynamics, ELK, Splunk.
• Experience with Nordic banks or payment providers.
• Older stacks for maintenance work: WebLogic, Tomcat, JSP, JavaScript, Bootstrap.
• Certifications: Oracle Java, Spring Professional, Kubernetes CKAD, cloud certifications.