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Freelance Senior Java Engineer · Java & Kotlin

Build and modernize business-critical Java and Kotlin applications.

I support teams in building and evolving reliable Java and Kotlin applications—from new features, services, and APIs to the incremental modernization of existing systems.

Java · Kotlin · Spring Boot · Jakarta EE · APIs · Microservices

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20+ years of experience · Banking · E-commerce · Healthcare · Public sector

Remote-first · On-site kick-offs and workshops when useful

Experience from complex projects across banking, healthcare, public services, e-commerce, and digital platforms.

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How I can help

Modernization

Modernize existing Java systems incrementally—from platforms and frameworks to persistence, supported by focused tests and comparisons.

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Application Engineering

Building and evolving reliable Java and Kotlin applications—from business logic and web applications to APIs, persistence, testing, and production delivery.

Integrations

Reliable interfaces and data flows between internal and external systems using APIs, messaging, and traceable operational processes.

Typical challenges

  • A business-critical Java application needs modernization
  • A team needs experienced support developing Java or Kotlin applications
  • Java, framework, or application-server upgrades are approaching
  • APIs, data flows, or integrations need stabilization
  • Technical change must happen while ongoing delivery and operations continue
  • Complex production issues, weak test coverage, or hard-to-maintain structures slow the team down

Selected project experience

Modernized a business-critical Java application

Migrated to Java 21, Jakarta EE 10, and Payara 6 through production deployment. This included around 30 new JPA entities, side-by-side operation with EJB 2, and an improved test setup.

Java 21 · Jakarta EE 10 · Payara 6 · JPA · Liquibase · JUnit

Evolved a business-critical banking application

Feature delivery, major-version upgrades, integrations, database migrations, automated testing, and build/deployment support in a regulated environment.

Java · Spring · Hibernate · Oracle · REST/SOAP · CI/CD

Built a scalable retail-media platform

Developing distributed Kotlin and Spring Boot services, internal and external REST APIs, data workflows, and cloud infrastructure for an integrated self-service platform.

Kotlin · Spring Boot · REST · AWS · Kubernetes · Terraform

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What you can expect when working with me

Experience with established Java systems

More than 20 years working with Java, Java EE/Jakarta EE, Spring, Hibernate, databases, and interfaces.

From planning through production

Modernization in defined stages, covering technical planning, hands-on implementation, testing, and coordination within the client team.

Experience in business-critical environments

Project experience across banking, public services, e-commerce, healthcare, and digital platforms.

Direct collaboration

Technical decisions and priorities are discussed directly with me, without agency handoffs.

Working together

I work as an experienced Senior Java Engineer within your existing team—including on long-term assignments—or take ownership of a clearly scoped application development, modernization, or integration project.

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