Stephan Liu

From cell culture to cloud.

I'm a biologist and bioinformatician who kept following the data: from the lab bench to Python scripts, from research servers to an OpenStack cloud, and now into systems programming at 42 Heilbronn.

What I want to do next is help organisations move their processes onto cloud infrastructure they can trust.

I started out in the lab.

Before I wrote software, I learned how science stays trustworthy: precise protocols, careful documentation and results that someone else can reproduce. That is still how I work.

B.Sc. Biology

University of Tübingen

Biology taught me to think in systems: cells, pathways and organisms, where small changes ripple through everything else.

As a research assistant in cell culture I worked to strict standard operating procedures. Every passage, medium change and deviation was documented, because one undocumented step can make weeks of work unreproducible.

That habit carries over directly to validated IT systems in regulated industries such as pharma, where proving a system does exactly what it should matters as much as the system itself.

M.Sc. Bioinformatics

University of Tübingen

Modern biology produces more data than any lab notebook can hold. In bioinformatics, biological questions become computational ones, and the answers depend as much on the pipeline and the infrastructure as on the biology.

This is where I shifted from using computers for science to building the systems science runs on. My thesis at the Center for Quantitative Biology (QBiC) ended up being an infrastructure project.

Automating lab analysis

Python, research assistant role

Recurring measurement series were analysed by hand in spreadsheets: slow, and easy to get subtly wrong. I replaced that with Python scripts that run the same analysis the same way every time.

This was a small project, but it was my first real piece of digital transformation: a manual process, made faster, less error-prone and reproducible by putting the logic in code.

Then the data needed somewhere to live.

For my master's thesis I went one layer down: away from the analysis and into the infrastructure underneath it.

OpenStack cloud for research data

Master's thesis, Cloud Computing Engineer at QBiC Tübingen

Research groups needed to exchange sensitive data securely between servers. I designed and operated an OpenStack-based private cloud (infrastructure as a service) to make that possible:

  • Keystone for identity and access, so only authorised users and services reach the data
  • Nova to provision compute instances on demand instead of hand-configuring servers
  • Neutron for segmented virtual networks, keeping traffic between projects isolated
  • Cinder and Swift for block and object storage
  • Encrypted transfer between servers, and continuous monitoring and tuning so it stayed stable under constant load
  • OpenStack
  • Linux
  • Virtual networking
  • IAM
  • Monitoring

Where I want to go: cloud and transformation.

Building that cloud showed me what interests me most: not one tool, but the moment an organisation changes how it works because its infrastructure finally lets it.

Cloud infrastructure

IaaS, identity and access management, network segmentation, storage. I've run these in practice, and I want to go deeper into hybrid and public cloud platforms and infrastructure as code.

From paper to platform

Labs and factories still run on spreadsheets, paper and isolated systems. I want to help map those processes, find the gaps and move them onto systems that scale.

Regulated by design

In life sciences, a system must be secure and also provably correct. I'm currently reading into GxP, GAMP 5 and computer system validation, so compliance is part of the design from the start.

Now I build software from first principles.

Since January 2025 I've been at 42 Heilbronn. There are no lectures and no teachers: you teach yourself each topic, build the project, and then other students review your code line by line before it passes. It's the most effective way of learning I've found.

  1. C and the Piscine

    Rebuilding the C standard library, memory and pointers, Makefiles and debugging from the shell.

  2. Unix and algorithms

    Processes, pipes and signals, sorting under constraints, and hardening a Linux server.

  3. Shells, threads, networks

    A bash-like shell built as a team, concurrency with mutexes, IP addressing and subnetting.

  4. miniRT

    A ray tracer in C: geometry, lighting and shadows from first principles.

  5. C++ Modules 00–07

    OOP from the ground up: orthodox canonical form, inheritance, polymorphism, exceptions, casts, templates.

  6. C++ 08 and Webserv

    STL containers, iterators and algorithms. Webserv, a small HTTP server in C++, is next.

    In progress, October 2026

miniRT: a ray tracer in C

42 Heilbronn, completed

miniRT renders 3D scenes from a plain-text scene file. For every pixel it sends a ray from the camera into the scene, works out what the ray hits first, and calculates how brightly that point is lit.

  • Ray intersection maths for spheres, planes and cylinders
  • Ambient and diffuse lighting, with hard shadows from a second ray cast towards the light
  • A parser for the .rt scene format that validates every value
  • Vector maths written from scratch, rendered to a window with MiniLibX

It's the most maths-heavy project I've done: linear algebra and geometry turned into working, testable code.

  • C
  • Linear algebra
  • Ray tracing
  • MiniLibX

The stack I build on.

Almost all of this I learned after my studies, at 42 Heilbronn and through self-study, working from the operating system upwards.

  1. Web

    • HTML semantic, accessible markup
    • CSS layout and animation without frameworks, like this site
  2. Applications and scripting

    • Python scripting, automation and data processing
    • Java object-oriented application development
    • Shell Bash scripting and daily command-line work
  3. Systems programming

    • C libc rebuild, a bash-like shell, threads, the miniRT ray tracer
    • C++ OOP, templates and the STL in the C++ modules
  4. Infrastructure and cloud

    • Linux server setup, hardening, administration
    • Networking TCP/IP, subnetting, virtual networks, sockets
    • Docker containerised services, reproducible environments
    • OpenStack a private IaaS cloud, built and operated
  5. Across every layer

    • Git version control and peer code review
    • Make build systems for every project

Beyond the code.

Abroad

I've lived in China, where I also gave some informal German lessons, and spent longer stays in the Czech Republic, Spain and the USA.

Languages

  • German, native
  • English, fluent
  • Chinese, B1

Let's talk.

I'm open to junior roles in cloud, IT consulting and software development, especially where life sciences meet technology.