Karsten J. Gerber

Staff Engineer & Systems Architect

About

I've been writing code since I was seven — typing little games from books into a Commodore 64 with a datasette. That was over 30 years ago, and I never really stopped.

Today I'm a software engineer based in Leipzig with 20+ years of professional experience across the full stack. From backend architecture and API design to frontends, mobile apps, and realtime systems — I've built and shipped software in teams of all sizes.

My main stack is Kotlin — backends with Ktor, frontends with KotlinJS, cross-platform with KMP. I've also worked extensively with PHP, JavaScript, Java, C++, and Flutter. My diploma thesis was a four-player chess engine in C++.

And still today I care most about making things work — clean architecture, robust systems, and code that doesn't fight back.

20+
Years experience
40+
Projects delivered
2
Awards won
200+
Concerts played

Experience

Creator

Klang Audio Motör
2026

Realtime cross-platform audio engine with 90%+ shared code across JVM and Web. Custom DSP stack, frame-precise scheduling, lock-free concurrency, and embedded scripting runtime.

Kotlin Multiplatform Web Audio API AudioWorklet DSP

Staff Engineer / VP Tech

The Base FOL Group
2020 – 2025 · Berlin

Architected and led development of a multi-tenant property management and community platform from greenfield to stable multi-year operation.

  • Full-stack architecture: backend, admin SPA, guest web app, mobile app
  • Scalable multi-property SaaS model
  • ~99.9% uptime on lean infrastructure
Kotlin/Ktor Java 17 Java 21 Spring Boot ArangoDB Postgres KotlinJS/Preact Flutter AWS

Freelance / Contract

Various
2012 – 2019

Backend engineering and architecture roles across multiple short-term engagements.

  • Rocklog GmbH — JVM, Clojure, Three.js (Switzerland, 2019)
  • DB Vertrieb GmbH — Databases, algorithms (Leipzig, 2018)
  • MagicInternet / MyVideo.de — PHP (2013–2014)
  • Gruner + Jahr — PHP, Java, FirstSpirit CMS (Hamburg, 2013)
  • Rocket Internet SE — PHP Core Team (Berlin, 2012)
PHP Java JVM Clojure FirstSpirit CMS Three.js SQL

Staff Engineer → CTO

ZipJet (Rocket Internet)
2014 – 2018

Joined at project inception. Built backend and infrastructure from prototype to first live city in 2.5 months. Later served as CTO.

  • Routing & last-mile optimization (>90% driver punctuality)
  • Scaled to multi-city operations
PHP Java 8 Spring Boot AngularJS React Native MongoDB

Software Engineer

3m5. Media GmbH
2006 – 2012 · Dresden

40+ web and multimedia projects for ZDF, Ravensburger, Audi, L'Oreal, O2, and more. Award-winning interactive games and platforms.

  • Goldener Spatz & GIGA Maus 2011 (ZDF Super-Bauwagen)
PHP/Symfony Flash/AS3 JavaScript C++ MySQL

Diploma in Computer Science

TU Chemnitz
1999 – 2006

AI specialization. Thesis: Chess engine for 4-player chess and game-theoretical analysis.

C++ AI Game Theory

Portfolio

Recent Work

Platforms, products, and tools I built from 2012 onwards — from startup CTOs to audio engines.

2026
2020 – 2025
2014 – 2018

3m5. Media GmbH Era

Interactive experiences for ZDF, Ravensburger, and others. 40+ projects in six years.

2011
2010
2009
2008
2007
2006

Open Source

Most of these started because I needed something and couldn't find it — or found it and didn't like it. All Kotlin, all actively maintained, all running in production somewhere.

Let's talk

Interested in working together? Drop me a line.

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