Nils Rommelfanger

Freelance Backend Software Engineer Continuous Delivery

📍 Amel, Belgium 📧 nils_rommelfanger@pm.me 📞 +32 (0) 456 950004

About Me

I am a software engineer with a strong Continuous Delivery mindset and 20 years of experience in backend technology. I bring a comprehensive skill set spanning architecture, clean code practices, automated testing, legacy code refactoring, deployment pipelines, operations, and observability.

I firmly believe that Continuous Delivery—TDD, feedback loops, and automation—are essential not only for delivering high-quality software but also for achieving high development efficiency. By continuously improving every aspect of the codebase, I ensure sustainable and efficient software development.

Most software spends far more of its life being read and changed than being written. Writing code that merely works today is the easy part; the harder—and far more valuable—skill is writing code that is still cheap to change next year. That is where I focus: readable, well-structured code, backed by tests that make change safe. The result is a lower total cost of ownership—fewer defects, faster changes, and less time spent deciphering what an earlier author intended—which is what justifies an experienced engineer’s rate.

Just as important as the code itself is clear communication. I see it as one of my core strengths: I ask the right questions to uncover what a requirement is really about, translate between business and engineering. Good software grows out of good conversations—and over years of remote and cross-cultural collaboration I have learned to keep those conversations clear, honest, and focused on the actual problem.

Core Competencies

Languages & Frameworks: Java • Kotlin • Spring Boot

DevOps & Cloud: Kubernetes • Docker • AWS • CI/CD (GitHub Actions, Jenkins) • Terraform • Helm • Infrastructure as Code

Architecture & Practices: Cloud Native • 12 Factor Apps • Microservices • Clean Code • Refactoring • Legacy Code Modernization • TDD

Testing & Quality: JUnit • Mockito • Automated Testing • Quality Assurance • Code Reviews

Observability & Security: Distributed Tracing (OpenTelemetry) • Logging • OAuth2/OIDC • Secure Coding

Databases & Messaging: PostgreSQL • MySQL • MongoDB • Redis • Apache Kafka • RabbitMQ

Methodologies: Agile • Scrum • Continuous Delivery • DevOps

Communication & Collaboration: Stakeholder Communication • Requirements Clarification • Bridging Business & Engineering • Mentoring & Knowledge Sharing • Remote & Cross-Cultural Teamwork • Technical Writing

AI-Assisted Development: Agentic Coding • Claude Code • AI Pair Programming • Prompt & Context Engineering —

Why Work With Me?

With 20 years of experience across diverse domains—from IoT platforms and autonomous systems to financial services and e-mobility—I bring deep technical expertise combined with a pragmatic, results-oriented approach.

What I Deliver:

  • Immediate Impact – I onboard rapidly and contribute from day one (joined projects 1 month before deadline and helped teams ship on time)
  • Fast, Efficient Delivery – I practice and promote CD principles, keeping software always release-ready so changes ship rapidly and efficiently while minimizing costly bugs and manual testing overhead
  • Lower Total Cost of Ownership – Code is read and changed far more often than it is written, so I optimise for the long game: readable, well-structured code backed by tests that make change safe. Fewer defects, faster changes, and easier onboarding mean the true cost of a feature keeps falling long after it ships
  • Legacy Rescue & Modernization – I turn struggling codebases into maintainable, efficient systems while keeping them stable
  • Scalable, Observable Systems – I build cloud-native architectures that are robust, performant, and easy to operate
  • Problem-Solver, Not Just Coder – I question requirements and challenge existing complexity. My focus is solving real problems, which often means simplifying or removing code rather than building more
  • Clear Communication – I ask the questions others don’t, translate between business and engineering, and make complex trade-offs easy to understand—so the whole team pulls in the same direction
  • AI-Augmented Delivery – I work effectively with agentic coding tools like Claude Code, applying the same engineering discipline—tests, reviews, clear requirements—to keep AI-assisted output fast and trustworthy
  • Deep Observability – Comprehensive logging and tracing reduce problem analysis effort and minimize mean time to recovery
  • Team Acceleration – I mentor developers and establish best practices that elevate entire teams

Whether you need someone to architect a greenfield project, rescue a critical system, or accelerate your team’s delivery—I’m ready to deliver results.

Professional Experience

Senior Software Engineer | European Commission - Health and Food Safety

March 2026 - Today

  • Rapid Onboarding & Impact: Contributing from day two. Taking responsibility for the project.
  • Improved the reliability of the tests and the pipeline.
  • Rapid Onboarding & Impact: Contributing from day two. Taking responsibility for the project.
  • Migrated authentication from an external dependency (frequently offline and a pipeline blocker) to a native Vert.x/Keycloak OAuth2 integration, eliminating the external dependency.
  • Implemented public and private search APIs with enum filters and DB projections (MongoDB) to reduce response payloads.
  • Built a BDD-enabled integration test framework with Testcontainers (Keycloak, MongoDB, HubStore). The tests are resilient to internal refactorings and describe business behavior.
  • Fixed flaky tests and made the pipeline reliable which was ignoring failed tests before.
  • Introduced OpenTelemetry tracing and structured logging for production observability.
  • Systematic refactoring: singleton elimination, explicit dependency injection and standardized error handling following RFC 9457. Fixed several bugs in the process.
  • Security hardening: global security baseline, role-based authorization and remediation of vulnerabilities and several security relevant bugs.
  • Worked extensively with agentic coding tools, established guardrails (tests, reviews, clear requirements) to keep AI-assisted output reliable, and supported colleagues in adopting them.
  • Upgraded Java from 17 to 26, cleaned up dependencies and consolidated the CI/CD pipeline.
  • Supported policy unit with quality control of another contractor.

Tech Stack: Java 26, Vert.x, Rest, JUnit, Mockito, Testcontainers, Behavior Driven Development (BDD), Acceptance Test Driven Development (ATDD), Test Driven Development (TDD), 12 Factor App, MongoDB, OpenApi, OAuth2, OpenID Connect, Keycloak, Continuous Delivery (CI/CD), Trunk Based Development, Refactoring, RFC 9457, Quality Assurance, Observability, OpenTelemetry, Distributed Tracing, Structured Logging, Slf4J, Logback, OpenRewrite, Agentic Coding, Claude Code, Kiro, Agile Scrum, Git, Gitlab, Secure Coding, Clean Code, Linux, Jira, Confluence

Senior Software Engineer | Actico GmbH

May - August 2025

Joined the project one month before deadline and immediately contributed from day 2, helping the team meet their goals comfortably.

  • Improved exception logging, reducing boilerplate by 80%
  • Addressed and resolved multiple bugs related to sorting and translation, improving system reliability and user experience.
  • Enhanced test quality to validate correct behavior
  • Implemented two critical features, including one at the core of the sanction list monitoring logic, improving the user experience.
  • Quality Assurance: I enhanced the test readability and quality with acceptance tests contributing to more robust and maintainable code and more stable tests.

Tech Stack: Java 17, Spring Boot, JUnit, Mockito, Postgres, Liquibase, JPA, Spring Security, Mapstruct, OpenAPI, Grafana, CI/CD

Senior Software Engineer | Ously Games GmbH

June - August 2024 (layoff due to financial problems)

  • Refactored codebase to remove unnecessary features and reduce maintenance overhead
  • Implemented reusable streak/mission/reward system to boost user engagement and retention

Tech Stack: Java 21, Spring Boot, JUnit, Mockito, MySQL, Liquibase, Redis, RabbitMQ, AWS, CI/CD

Cloud Engineer | Morgenwerk GmbH

June 2023 - March 2024

Developed navigation algorithm for warehouse AGVs from scratch.

  • Designed adapted A* algorithm for planning hundreds of robots in 3D storage space with >99% storage density
  • Performance tested for up to 10,000 AGVs
  • Comprehensive testing with JUnit and Mockito
  • Implemented deployment pipeline with GitHub Actions

Tech Stack: Kotlin, Spring Boot, JUnit, Mockito, AWS, MQTT, A* algorithm, CI/CD

Senior Software Engineer | Clevershuttle

April 2022 - May 2023 (company bankruptcy)

Platform for on-demand shared rides.

  • Developed microservices with Spring Boot and Kotlin
  • Designed and implemented multi-tenancy support
  • Improved test coverage and observability (OpenTelemetry)
  • Provided mentorship to junior developers
  • Contributed to architecture decisions

Tech Stack: Java 17, Spring Boot, Kafka, MongoDB, Kubernetes, AWS, GitHub Actions, CI/CD

Senior Software Engineer | Bosch.IO

2008 - 2022

Worked on multiple internal IoT projects including:

Robert Bosch Semantic Stack

Comprehensive product lifecycle data platform.

  • Developed catalog microservice
  • Architecture and design work
  • Ensured CI/CD with automated testing

Tech Stack: Java 11, Spring Boot, Spring Security, Kubernetes, Docker, AWS Neptune, RDF, OAuth2, OpenTelemetry

Bosch IoT Suite Portal

User and subscription management for SaaS offerings.

  • Full-stack development and operations
  • Implemented org/team-based access management
  • Refactored legacy codebase
  • Mentored junior developers

Tech Stack: Java 11, Spring Boot, Hibernate, Kubernetes, Docker, Thymeleaf, AWS, OAuth2, Ory Hydra, New Relic, Dynatrace

Central Authorization Server

OAuth2-based authentication/authorization replacement.

  • Designed and built authorization server (Keycloak → Ory Hydra)
  • Built REST API for resource registration
  • Analyzed and resolved scalability issues
  • Migrated from EC2 to EKS
  • Infrastructure as Code with Terraform and Helm

Tech Stack: Java 8, Spring Boot, Kubernetes (EKS), Terraform, Helm, OAuth2, Keycloak, Ory Hydra, Distributed Tracing

Bosch Permission Service

SaaS authentication and authorization solution.

Tech Stack: Java 8, Spring Boot, PostgreSQL, Docker, Jenkins, Splunk, ELK Stack

Bosch Thermotechnik

B2C/B2B portal for heating appliances.

  • Backend development
  • Remote collaboration with teams in Germany and Portugal

Tech Stack: Java 8, Vert.x, MongoDB, RabbitMQ, Cloud Foundry, OSGI

Indego Autonomous Lawn Mower

Backend for cloud-connected lawn mowers.

  • Sole developer for ~1 year
  • Designed smart mowing based on weather forecasts
  • Implemented OTA firmware update management
  • Performance profiling and comprehensive logging

Tech Stack: Java 8, Vert.x, RabbitMQ, Cloud Foundry, MongoDB, Splunk, ELK Stack

E-Mobility Charging Broker

Unified billing across charging providers.

  • Introduced application logging from scratch

Tech Stack: Java 8, Spring, Tomcat, Oracle Cloud Foundry

Additional Projects

  • Telemedicine: Migrated SQL to Hibernate/Criteria API
  • Finance Suite (Vontobel Bank): Maintained 12-year legacy codebase, optimized complex Hibernate/SQL queries
  • Finance Suite Product: Transaction monitoring for compliance and fraud detection

Earlier Roles

Software Engineer | Indextraffic (2007-2008) Co-founder - Portal engine for SEO-optimized pages

Software Engineer | Suchtreffer (2005-2007) Backoffice tools for AdWords campaigns and custom ORM mapper

Education

Diplom Informatiker (FH) | HTWG Konstanz 2001-2005: Software Engineering - Artificial Intelligence 1999-2001: Technische Informatik

Allgemeine Hochschulreife | Bodensee Gymnasium Lindau 1990-1997

Languages

  • German: Native
  • English: Fluent

Interests

Family • Cooking • Gardening • Technology • DIY

Let’s build something great together.