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📂 References & case studies

Projects that were stuck – and are running now

No glossy sales decks, just real starting points: an old PHP monolith, a Java 8 system without tests, and an AI prototype without security. Here is what became of them.

🔹 Fixed price. 4–6 weeks delivery. You keep the code.

Discuss your project → View case studies
🏆 3 documented projects
⏱️ 4–6 weeks delivery
🤝 Also available as subcontractor for agencies
PHP → React Java 8 → Spring Boot 3 AI prototype → production

❌ "Our frontend is stuck inside the old PHP monolith"

❌ "Every change in the Java 8 system is a risk"

❌ "The AI prototype has no auth and no tests"

✅ Solution: step-by-step modernization without downtime

Concrete results

Three projects, three rescued systems

Every case study shows the starting point, the approach and a measurable result. Pick the project that is closest to your situation.

Agency subcontractor

PHP monolith → React/Next.js

Task: A modern frontend for an old PHP backend – without replacing the backend.

Duration5 weeks
ModelFixed price
RoleSubcontractor
Result60 % faster
React Next.js TypeScript REST API
View case study →
Legacy modernization

Java 8 → Spring Boot 3

Task: A 15-year-old Java 8 monolith needed to be modernized step by step.

Duration6 weeks
ModelFixed price
RoleFreelancer
Resultmaintainable & tested
Java 8 → 21 Spring Boot 3 JPA CI/CD
View case study →
AI refactoring

AI-generated code made production-ready

Task: An AI-generated prototype had to become production-ready – with auth, tests and deployment.

Duration4 weeks
ModelFixed price
RoleFreelancer
Resultlive for real users
React Node.js JWT auth CI/CD
View case study →
Results at a glance

What you actually end up with

No buzzwords – just numbers that change something in day-to-day business.

60 %faster development after the frontend rebuild
0outages during the migrations
4–6 wkstypical delivery time at a fixed price

🔧 Subcontractor for agencies

You have a client who needs legacy modernization or AI refactoring – but your team has no capacity or expertise? I work as a reliable subcontractor for agencies and IT service providers. Fixed price, clear communication, on-time delivery – and you stay the single point of contact for your client.

  • Confidential and on behalf of your agency – no poaching of end clients
  • Firm deadlines and a clearly defined scope before kickoff
  • Handover with documentation, tests and a clean Git history
Get in touch now →
Before / after

From chaotic to production-ready

📉 Before: PHP monolith with 12k lines, no testing, constant outages.

📈 After: API-first architecture + React dashboard, outage rate −95 %.

✓ Legacy modernization in 6 weeks

🤖 Before: AI-generated React app without a backend – data stored only in localStorage.

⚡ After: Complete Java/Spring API, PostgreSQL, JWT auth + clean UI.

✓ AI integration & going live
Why clients hire me

Because reliability matters more than hype

  • Fixed price instead of hourly risk – you know the number before we start
  • Ongoing operations keep running – the migration happens without downtime
  • You keep the code: properly documented, tested and ready to hand over
  • Direct communication with the developer – no agency layers in between

Instead: architecture, stability and a UI that actually works.

"I already had 3 AI prototypes built – not one of them runs in the cloud."

– That is exactly where I take over.

Portrait of Joerg Loos, freelance full-stack developer for legacy modernization and AI integration
About me

Your technical sparring partner for difficult software projects

I support companies when legacy systems slow everything down or AI prototypes are not production-ready. The projects above came out of exactly these situations – with clear architecture, solid tests and traceable results.

Stack: Java, React, PHP, Spring Boot, Node.js • Approach: pragmatic, transparent, production-focused.

Your project could be the next one

Let's talk for 30 minutes free of charge – I will analyze your legacy or AI case and tell you honestly whether I can help.

Go to inquiry form →

🔹 Fixed price? Yes, of course. Just ask.

or via LinkedIn / Xing — contact details on request