Senior API Developer – Java & Cloud Services

Ignite innovation with scalable APIs — shape the future of banking technology.

Krakow-based opportunity with hybrid work model.

As a Senior API Developer – Java & Cloud Services, you will be working for our client, a leading financial institution dedicated to transforming digital banking. You will design, build, and optimize secure, scalable APIs that power their cutting-edge digital products and internal platforms, leveraging modern Java and cloud-native patterns to deliver impactful solutions swiftly and reliably. This role offers an excellent platform for technical growth and innovation in a dynamic financial environment.

Your main responsibilities:

• Build and evolve high-performing, scalable APIs and backend services using Java, Spring Boot, and Maven (developed primarily in IntelliJ).
• Collaborate with cross-functional teams, including engineers, product owners, architects, and testers, to deliver robust services aligned with business needs.
• Design APIs following industry standards (REST, GraphQL, SOAP), ensuring versioning, backward compatibility, and optimal consumer experience.
• Integrate with third-party and internal APIs, ensuring resilience, observability, and clear error handling.
• Develop and support event-driven services utilizing Kafka, managing topic design, schema evolution, and message reliability.
• Deploy cloud-ready services on AWS, including Kubernetes / EKS, Fargate, Redis, RDS, S3, Route 53, with consideration for deployment and runtime environments.
• Maintain product quality through automated testing, regular API testing, and troubleshooting live issues with a "you build it, you run it" approach.
• Produce comprehensive API documentation using OpenAPI/Swagger and supporting runbooks as necessary.
• Contribute to engineering standards around security, performance, maintainability, and continuous improvement.

You're ideal for this role if you have:

• At least 5 years of hands-on experience building APIs and backend services in Java.
• Strong expertise with Spring Boot and Maven.
• Solid understanding of backend architecture concepts including service design, data access, caching, and resilience.
• In-depth knowledge of API styles and integration patterns (REST, GraphQL, SOAP).
• Experience working with API tooling such as Postman, Swagger UI / OpenAPI, SoapUI.
• Ability to work with data formats like JSON and XML.
• Proven troubleshooting skills to diagnose issues, fix defects, and enhance performance and reliability.
• Strong collaboration skills and ability to communicate technical decisions effectively.

It is a strong plus if you have:

• Experience with event-driven architecture at scale (Kafka streams, schema registry, idempotency, exactly-once/at-least-once).
• Familiarity with AWS services like Kubernetes/EKS, Fargate, Redis, RDS, S3, Route 53.
• Knowledge of CI/CD pipelines, observability tools (logging, metrics, tracing), and secure coding practices.
• Strong critical thinking and a pragmatic, delivery-focused mindset.

Language Required for the role:

• Fluent English (spoken and written).

Eligibility for the role:

• Only candidates with an existing legal right to work in the European Union will be considered for this role.

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Interested? Apply now and include your CV (preferably in English) along with a statement confirming your consent to the processing and storage of your personal data.