I'm an experienced leader & product-minded engineer deeply interested in collaboratively building useful products. With a backround spanning from small startups to scaling unicorns, I bring a wealth of experience in Elixir, Ruby and SQL complemented by JavaScript. I love Open Source, participating in the community and giving talks. My passion for performance optimization and benchmarking led me to create benchee.
In my most recent role as a Senior Staff Engineer, I led teams to success by removing obstacles, fostering a culture of collaboration and filling the gaps. Whether managing a product department of 15 or mentoring junior developers, my greatest joy comes from empowering others. I am fascinated by the human side of software development and continually strive for the optimal balance between immediate value delivery and long-term sustainability.
Screenverse
(~40 employees)
06/2024 — now
Worked in programmatic digital out of home advertisement using Elixir to ship performant & reliable software.
- Built a "fancy" proxy server (caching, enrichment, response time guarantees) serving ~84 Million requests per day (peak: ~2000 RPS) on a single 4-core server using Elixir, GenServer, ETS & Plug
- Iteratively extended functionality to parse XML responses (Rust) & more permanent cache (Redis/Valkey)
- Pushed initiatives like developer learning, standardization, test coverage & reducing error fatigue
- Proud recipient of the "Chat Wizard" award
Remote
(~150 → 1100 employees)
04/2021 — 10/2023
Worked on a big Elixir & Phoenix monolith in HR-tech with a focus on the payments domain, automating processes to ensure safe, quick & reliable payments of millions while improving processes and technology company wide.
- Implemented features to help our payments efficiency and product offering: automatic invoice payments, bank integration via PAIN XML to automate payments, enable direct debit for huge sums & allowing non local currencies
- Design and implementation of central payment projects aiming to incorporate more providers
- Most senior engineering individual contributor for a long time, involved in high level technology decision making
- Introduced Background Job System (Oban) to guarantee reliable asynchronous execution
- Improved processes such as branching strategy (death to long lived branches!) and the RFC process itself
- Advocated for hiring non Elixir engineers & setup a training camp and mentoring structure to help them succeed
Shopify
(~8000 employees)
08/2020 — 03/2021
Engineering Lead for a team working in Ruby on Rails on topics ranging from local market adaptation, to legal and delivery promise in the e-commerce field.
Self-employed
08/2019 — 07/2020
Consulting, Teaching and Development.
- Helped a company develop their first Elixir project, introducing the technology to the team
- Loadtested a Rails ecommerce system leading to 100x the number of concurrent checkouts with fewer servers
- Worked on a complex microservice metrics visualization application in Ruby & NodeJS
- Open Source work on the code coverage tool SimpleCov sponsored by Ruby Together
- Consulted on the design, architecture & implementation of an open source project, including implementation
Liefery
(~50 → 150 employees)
01/2017 — 2/2019
Led a product department of 15 together with the CTO, handling the day-to-day needs of the team. Built and maintained applications to track shipments, plan tours and manage all required logistics data in Ruby on Rails, Elixir and Phoenix as well as JavaScript (AngularJS, React).
- Helped, mentored & guided colleagues through 1o1s, pairing sessions, pull request reviews and knowledge sharing sessions
- Ran retrospective and iteration meetings, continuously adapting and improving processes
- Architected and designed features with the squads
- Served as interim-CTO during a sabbatical
- Monitored application performance and fixed performance problems
- Screened and interviewed candidates
- Gathered issues from operations and partners to define and triage solutions
- Ran integration projects with customers to onboard them as quickly as possible
bitcrowd
(~10 employees)
01/2015 — 10/2016
Built various applications with Ruby on Rails, AngularJS & React in this agency setting. Introduced practices such as retrospectives, Continuous Integration and mentored juniors.
Self-employed
05/2013 — 09/2018
Occassional projects related to teaching programming, such as an introductory course at Humboldt-University Berlin.
Conferences
05/2012 — current
I like to speak at conferences to share knowledge and spread ideas. I have spoken at conferences such as Øredev, Lambdadays, Polyconf and Full Stack Fest (overview of my talks).
- In 2024 I keynoted Code BEAM EU with "Going Staff"
- My talks cover a wide range, from Benchmarking to "Functioning Among Humans"
- One of the main organizers and host for Devs for Ukraine (2022)
- Head organizer JRubyConf 2015 & organizer eurucamp 2015, was a member of the program committee of GOTO Berlin 2014
Open Source
08/2011 — current
I live and breathe Open Source and contribute to a variety of projects big and small. This is a selection of bigger projects I maintain or maintained.
- benchee a powerful and extensible benchmarking library for elixir and erlang
- simplecov the popular ruby code coverage tool
- Shoes an easy to use GUI toolkit written in JRuby that I also worked on as part of Google Summer of Code
Ruby User Group Berlin
10/2012 — current
A monthly meetup about Ruby and related technologies, with anywhere between 40-120 attendees. Co-created the Berlin Code of Conduct to ensure and promote a safe environment.
Rails Girls / code curious
06/2012 — 12/2024
Rails Girls helps to diversify the tech community by helping beginners to get in touch with programming. I coach at workshops and since 2013 I also coach a weekly project group, the rubycorns, helping attendees grow into Juniors & beyond.
Hasso Plattner Institute / Blekinge Institute of Technology (Erasmus)
2008 — 2014
Final grade: 1.2 (A), Specialization in Software Architecture, Internet Security, agile & globally distributed software development
Enginneering Practices
- agile Software Development (XP/Scrum/Kanban)
- Test Driven Development (RSpec, ExUnit, Jasmine...)
- Pair Programming
- Version Control (git)
Programming
- Object Oriented Programming (Ruby, Smalltalk)
- Functional Programming (Elixir, functional JavaScript)
- Web frameworks (Ruby on Rails, Phoenix)
- Benchmarking & Performance Improvements
- Web Technologies (HTML, CSS, JavaScript, JSON...)
Leadership & Communication Skills
- Run and moderate meeetings such as Retrospectives
- one-on-ones
- Mentoring and Teaching
- Empathy
- Eye for process improvements and bottle necks
System Architecture
- Database Design (SQL)
- Domain Driven Design
- Design Patterns
- Monoliths, microservices and the in-between
- APIs (modules, REST)