ATL/Technical Lead - Java

About Gapstars

At Gapstars, we partner with some of Europe’s most ambitious tech companies, from disruptive startups to fast-scaling scaleups, helping them build high-performing remote engineering teams. Headquartered in the Netherlands, with talent hubs in Sri Lanka and Portugal, we are home to 275+ engineers who thrive on solving real-world challenges with modern technologies. Our teams work across domains, from networking and marketplaces to SaaS and AI, delivering scalable solutions that drive meaningful outcomes. If you’re looking for a company that combines technical excellence, a strong culture, and room to grow, welcome to Gapstars.

About the Role

Client is looking for a hands-on Senior Java Developer (ATL/TL level) to take ownership of a complex, legacy Java application landscape running across ~20 servers. The environment uses an older version of GlassFish and has limited documentation. The main challenge is to understand, document, and maintain application-level integrations (how services connect and interact), stabilize the platform, and prepare the ground for future modernization/migrations.

This is not an operations-first system role; it is a development + integration ownership role with strong emphasis on technical discovery, documentation, and legacy platform stewardship.

Key Responsibilities

• Take ownership of a legacy Java platform from an application + integration perspective.

• Discover, map, and document:

  • application dependencies, integration points, data flows, interfaces, deployment topology (as relevant), and key runtime/config assumptions

• Analyze and resolve complex production issues related to:

  • Java application behavior, performance bottlenecks, runtime issues, integration failures, and stability concerns

• Work with (and gradually build confidence in) the legacy runtime environment, including GlassFish configuration and deployments.

• Improve maintainability through:

  • clear technical documentation, diagrams, runbooks (where useful), better logging/observability recommendations, and incremental refactoring when appropriate

• Support and guide engineering standards as an ATL/TL profile:

  • code reviews, mentoring, technical guidance on integration design and legacy-safe improvements

• Collaborate closely with stakeholders to create a shared understanding of “how the platform works” and support migration readiness.