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Freelance Senior Backend Engineer · Java & Kotlin

Modernize business-critical Java systems. Verify the behavior that matters.

I take on the incremental evolution of your application, from assessment through implementation and verification. I combine extensive migration experience with automated transformations and targeted use of AI.

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

Discuss modernization View references

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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Clue

What I’m hired for

Modernization

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

Explore my approach

Backend Engineering

Building and evolving reliable Java and Kotlin backend services, including APIs, persistence, testing, and production delivery.

Integrations

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

Modernization approach

1. Understand the system

Identify dependencies, critical workflows, and technical constraints.

2. Capture reference behavior

Use and strengthen existing tests, capturing relevant results and measurements as a comparison baseline.

3. Migrate incrementally

Implement small, reviewable changes and automate repetitive work where useful.

4. Compare and stabilize

Repeat relevant scenarios, investigate unexpected differences, and document intentional changes.

A strong fit when …

  • a business-critical Java application needs modernization
  • a team needs experienced Java or Kotlin backend support
  • 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 20–30 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 take ownership of a clearly scoped modernization engagement, or work as an experienced engineer within your existing team, including long-term assignments. An assessment with a staged plan or standalone migration verification offers another starting point.

Discuss modernization