Java Developer - Core Banking

Senior Java Engineer – Core Banking
6-month contract
Fully Remote
Outside IR35 £400 per day

We are looking for a Senior Java Engineer to join a major Core Banking team delivering the development, modernisation and support of mission-critical banking services.

You will work across several strategic initiatives, including core banking transformation, legacy-system modernisation, regulatory enhancements and integrations between core banking platforms and surrounding services.
This is a hands-on engineering position requiring strong Java expertise and recent experience delivering highly available systems within banking, payments or financial services.

Key responsibilities

• Design, develop and maintain Java and Spring Boot services supporting core banking operations.
• Modernise legacy banking applications into scalable microservices.
• Build APIs and event-driven integrations between core banking platforms, payment systems and third-party services.
• Develop services covering areas such as accounts, balances, transactions, payments, reconciliation and regulatory reporting.
• Maintain transaction integrity, resilience, security and performance.
• Implement automated unit, integration and contract testing.
• Troubleshoot production incidents and perform root-cause analysis.
• Participate in code reviews, technical design and architecture discussions.
• Collaborate with architects, product owners, analysts and other engineering teams.
• Support the delivery of regulatory and compliance-driven banking changes.

Essential experience

• Strong commercial Java development experience, ideally Java 17 or 21.
• Extensive experience with Spring Boot and microservices.
• Recent experience within core banking, digital banking, payments or financial services.
• Experience building mission-critical, high-volume transactional systems.
• Strong REST API and systems-integration experience.
• Event-driven development experience using Kafka or similar technologies.
• Strong SQL and relational-database knowledge, such as PostgreSQL or Oracle.
• Understanding of distributed-system patterns, including idempotency, retries, reconciliation and failure recovery.
• Automated testing experience using JUnit, Mockito, Testcontainers or equivalent tools.
• Experience with Docker, Kubernetes and CI/CD pipelines.
• Strong communication skills and the ability to work within an international delivery team.

Desirable experience

• Experience with platforms such as Temenos Transact/T24, Oracle FLEXCUBE, Finacle, FIS, Fiserv, Mambu, Avaloq or a bespoke core banking system.
• Core banking transformation, migration or legacy-modernisation experience.
• Knowledge of account servicing, ledgers, balances and transaction posting.
• SEPA, SWIFT, Faster Payments, CHAPS, BACS, Instant Payments or ISO 20022 experience.
• AWS, Azure or GCP experience.
• Exposure to regulatory initiatives such as PSD2, Open Banking, DORA, AML or GDPR.
• Production support or on-call experience for critical banking services.

This is an excellent opportunity to join a significant banking transformation programme and work with modern Java, cloud and distributed-system technologies.