Overseas Contractor- Senior Java Backend Developer

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

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 AIassisted 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 eventdriven 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 AIassisted design code generation and testing

Use AI coding assistants and agents eg GitHub Copilot Spec Kit or similar to turn specifications into plans tasks code and tests Critically review all AIgenerated 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 AIassisted 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 OAuth2OIDC JWT and mTLS

Microservices patterns API gateway circuit breaker saga outbox CQRS and event sourcing

Kafka producers consumers partitioning schema registry Kafka Streams

Contractfirst REST API development OpenAPISwagger API versioning and documentation

Payments domain

Handson experience with ISO 20022 messages pain pacs camt and SWIFT MTMX migration

Knowledge of SEPA Credit Transfer SEPA Instant SCT Inst SEPA Direct Debit and realtime payment schemes such as TIPSRT1

Understanding of the payment lifecycle initiation validation screening routing clearing settlement and reconciliation

Awareness of EU regulation including PSD2Open Banking APIs the EU Instant Payments Regulation DORA GDPR and AMLsanctions screening

AI and specdriven development

Practical experience with specdriven development writing structured testable specifications that drive AIgenerated 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 AIgenerated 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 BambooJenkinsGitHub 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 SASTSCA OWASP Top 10

Shell scripting and scheduling tools UC4Automic AutoSys ControlM

Ways of working

Experience in Agile and SAFe delivery

Good to Have

Cloud platforms Azure AWS GCP

Observability Grafana Prometheus OpenTelemetry AppDynamics ELKSplunk

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