~/portfolio $
I build fast,
reliable web apps._
> Freelance backend developer with 2+ years of experience turning complex ideas into clean, scalable products. From MVP to production.
About me
The person behind the code
Hi, I'm Yannik, a freelance backend developer specializing in Java and Spring Boot. I love turning complex business requirements into clean, maintainable systems while always keeping security, scalability, and shipping in focus.
Selected work
Recent projects
Open-source and personal projects — from production-grade backends to creative experiments.
Document Distribution Application
An application for the structured management and distribution of documents. It supports versioned data storage, role-based access control, and the import and export of data in common file formats.
Not publicPersonnel Management Application
An application for managing personnel master data with a multi-user architecture. It offers role-based access control and export functions for further processing of data in Excel.
Not publicTeam and Workspace Management Platform
A web-based platform for managing teams and workspaces with a multi-tenant architecture. It lets different organizations use it as separate tenants and provides modern authentication via OAuth. The application was built as a ground-up rebuild of an existing system, including the migration of legacy data into the new architecture.
Visit site →Control and Measurement Software for Testing Machines
Software for controlling and acquiring measurement data for industrial testing machines. It consists of a Java-based machine controller and a web application, and enables running and evaluating test procedures directly at the machine.
Not publicSpring RBAC Showcase
A Spring Boot reference application demonstrating multi-tenant, role-based access control on top of essencium-backend. Models organizations → projects → tasks as a REST API, with every endpoint guarded by fine-grained rights.
View on GitHub →Elysian Fantasy Map
Interactive fantasy world map for a novel, built with Leaflet.js. A creative hobby project combining cartography and storytelling.
Not public yetServices
What I do
Backend development for multi-user systems with robust permission and role management.
Backend
Java, Spring Boot, REST APIs. Scalable server-side architecture built for growth.
Database
PostgreSQL, schema design, migrations, and query optimization for reliable data layers.
Integration
Third-party APIs, and service connectors to tie your systems together.
RBAC
Role-based access control and permission management for secure multi-user systems.
Tech stack
Tools of the trade
Battle-tested technologies I reach for to get the job done well.
Partners
Successful partnerships
Companies I have partnered with to build and ship reliable software.
Testimonials
What clients say
Feedback from the people I have built software for.
We have been collaborating with Yannik on our projects for several years now. He has always been a reliable partner and colleague who quickly integrates into our development team and actively drives projects forward. What I particularly appreciate about him is his calm, thoughtful manner and the initiative he takes in approaching and solving problems in a structured way. Especially in our most recent major project, Yannik was a key contributor and played a major role in its successful implementation. I always enjoy working with him.