Overseas Contractor- Senior Backend developer

LTM; Gdynia; Hybrid; PLN 180,000 - 300,000; Full time

Job summary

LTM in Poland seeks a Senior Java Backend Developer with payments experience to design and build secure, high-performance payment services, leveraging Core Java, Spring Boot, microservices, and Kafka in a hybrid setup between Gdynia and Warsaw.

You will drive AI-assisted spec-driven development, turn specifications into plans, code, and tests, and own solutions from spec through production while collaborating with Nordic client stakeholders in an Agile SAFe environment.

Qualifications

• 10 years in Java backend development
• 5 years in payments or banking
• Hands-on experience with payments domain including ISO 20022 messaging and real-time schemes

Responsibilities

• Design, develop and maintain scalable payment microservices for initiation, clearing, settlement, and reconciliation
• Build event-driven flows using Kafka with idempotency, exactly-once processing, retries, and error handling
• Write specifications, requirements, acceptance criteria, API contracts, data models and use them as the source of truth for AI-assisted design, code, and tests
• Use AI coding assistants to turn specs into plans, tasks, code and tests; review AI outputs for quality and security
• Design REST APIs contract-first using OpenAPI and keep specs and code in sync
• Ensure banking-grade security, resilience, auditability, and data protection
• Mentor peers on modern Java and AI-assisted engineering; work in Agile SAFe teams
• Support production and analyze incidents for business-critical payment systems

Skills

Core Java

Spring Boot

Microservices

Kafka

AI-assisted engineering

OpenAPI

Security

Agile SAFe

Tools

Docker

Kubernetes

GitHub Copilot

OpenAPI/Swagger

Maven

Job description

Role Description

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