Application audit
I review the code, architecture, dependencies, database and deployment. You get a written report: what is on fire, what can wait and how much the modernization will take. Scope and price are agreed up front.
Senior .NET Developer · Freelance
I keep older .NET applications running and bring them up to date.
I'm Martin Hájek. For twenty years I have been building and maintaining business systems in .NET, twelve of them for the public sector. I help companies whose important application runs on the old .NET Framework and who have no one left to look after it.
- 20 years with .NET
- fully remote, EU time zones
- direct, no middleman
- Czech and English
Services
We usually start with an audit. Afterwards you know what state the application is in and can decide what to do next – with me or without me.
Step-by-step modernization
From .NET Framework, WCF or WebForms to current .NET in small steps, without a big rewrite. Every step is backed by automated tests, the application keeps running the whole time and users barely notice.
Development and maintenance
New features, fixes and taking over code from someone who has left. Happy to work on a part-time or fixed-term contract, on my own or as part of your team.
Experience
Most of my career has been spent on large systems that have to run for years and must not break.
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12 years
Public sector – Czech Social Security Administration and ministries
Development, maintenance and evolution of large case-management systems. Long life cycles, strict security and documentation requirements, hand-overs between teams and vendors.
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since 2024
Modern .NET
.NET 8 and 10, Angular, Clean Architecture and modular monoliths. Docker, CI/CD in GitHub Actions and cloud deployment.
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15 years
Freelance
Self-employed, used to owning both the deadline and the result.
Selected projects and clients
eNeschopenka
Czech Social Security Administration
The national electronic sick-leave system used by doctors across the Czech Republic. I worked on the Social Security Administration's part.
Mapy.cz
Seznam.cz
The leading Czech map portal. I built the entire frontend and database layer on my own; map rendering was done by another team.
Other clients
- O2 Czech Republic (formerly Telefónica O2) – CRM
- Provident Financial – call centre information system
- OZP – a Czech public health insurance company
Work sample
Public-sector code belongs to the clients and I can't show it. That's why I have a project of my own you can look through in full.
WakePark
A booking system and online shop for a wakeboarding park. It runs in production, sells vouchers and all the code is public on GitHub (documentation in Czech).
- modular monolith in .NET 10 and PostgreSQL, eight modules
- over 300 automated tests: business rules, integration against a real PostgreSQL database, and architecture rules guarding module boundaries
- QR payments matched automatically from the bank, tax invoices and PDF vouchers
- every green change deploys itself via GitHub Actions and Docker
- key decisions written down as ADRs, trade-offs included
How I work
- Directly with meNo agency and no agency margin. The person you agree with is the one who does the work and stands behind it. You always know what is done and what comes next.
- Tests as a safety netBefore I touch legacy code, I cover its current behaviour with tests. Then I change it in small steps and nothing breaks silently.
- Decisions on paperWhy something was built the way it was can be traced even five years later.
- AI tools, openlyI use them to move faster. I still stand behind every line of code.
Let's talk
Send me a few lines about your application and what's bothering you. I'll reply within two working days.
martin.hajek@centrum.cz