Senior Java Integration Lead - API, IBM MQ & Mainframe

emagine; Województwo mazowieckie; Hybrid; PLN 180,000 - 300,000; Full time

Job summary

emagine is seeking an experienced Senior Java Integration Developer to support enterprise integration layers for payment initiatives. You will own API design and implementation using Java/Spring Boot, REST, and OpenAPI, connecting digital apps with backend and mainframe systems in a hybrid Warsaw setup.

This hands-on role requires end-to-end ownership, mentoring teammates, and producing clear technical docs as the project starts in December 2026 for a minimum 6 months.

Qualifications

• Strong hands-on experience with Java and Spring Boot.
• Senior-level backend or integration development experience.
• Strong experience designing and implementing REST APIs.
• Very good knowledge of OpenAPI / Swagger and API contracts.
• Practical experience with IBM MQ or a comparable enterprise messaging technology.
• Good understanding of asynchronous communication and enterprise integration patterns.
• Experience with data mapping, validation and error handling.
• Experience deploying applications in containerised or PaaS environments.
• Strong troubleshooting and analytical capabilities.
• Ability to work independently and take technical ownership.
• Willingness and ability to mentor developers and transfer knowledge.
• Good English communication skills.

Responsibilities

• Design REST APIs using Java and Spring Boot.
• Work in contract-first API development with OpenAPI/Swagger.
• Translate API contracts into production-ready implementations.
• Build integrations connecting digital apps with backend and mainframe systems.
• Develop integrations using IBM MQ or comparable messaging tech.
• Implement reliable asynchronous message exchange.
• Design data mappings and transformation logic.
• Implement validation, error handling and failure scenarios.
• Support deployment within containerised / PaaS environments.
• Mentor and transfer knowledge to team members.
• Prepare technical documentation and handover materials.

Skills

Java

Spring Boot

REST APIs

OpenAPI/Swagger

IBM MQ

Asynchronous messaging

API contracts

Job description

emagine is seeking an experienced Senior Java Integration Developer to support enterprise integration layers for payment initiatives. You will own API design and implementation using Java/Spring Boot, REST, and OpenAPI, connecting digital apps with backend and mainframe systems in a hybrid Warsaw setup.

This hands-on role requires end-to-end ownership, mentoring teammates, and producing clear technical docs as the project starts in December 2026 for a minimum 6 months.