Dušan Dželebdžić
I modernize the systems your business can’t live without.
30 years with legacy systems, modern stacks, and the integrations between them. When things stop working, I make them work again. Fast.
- OpenVMS
- DCL
- COBOL
- Linux
- AWS
- Terraform
- PostgreSQL
- MySQL
- PHP · Symfony
- TypeScript · NestJS
- Python
- React · Next.js
- Swift
- Docker
Problems I get called in for
Usually after something has already broken, or when everyone is too scared to touch it.
- Legacy systems nobody understands anymore
- Migrations that are too risky to touch
- Systems that need to talk to each other but don’t
- Production going down or behaving unpredictably
- Infrastructure that doesn’t scale or randomly fails
- Performance issues under real-world load
Root causes, not symptoms.
Client names stay private. The failure modes don’t, because the next team will hit them too.
| NO. | SYMPTOM | ROOT CAUSE | AREA |
|---|---|---|---|
| 001 | Production outage affecting thousands of users | Cascading connection-pool exhaustion across microservices | ARCHITECTURE |
| 002 | Multi-server WordPress stack with recurring crashes | Memory leaks in custom plugins and misconfigured caching layers | WORDPRESS |
| 003 | Cloud-to-on-prem MySQL replication failing silently | MTU mismatch and packet fragmentation between networks | NETWORKING |
| 004 | An AWS bill thousands a month higher than it should be | Oversized instances, forgotten snapshots, unattached EBS volumes | AWS |
| 005 | Deployment pipeline down, under time pressure | Dependency conflict in the CI/CD chain. Fixed and shipped the same day | CI/CD |
How to work with me
Legacy modernization
Your business runs on a system nobody dares to touch. I connect it to modern infrastructure, move the data out piece by piece, and retire it on your schedule, not on the day it finally dies. From OpenVMS to last decade’s PHP monolith.
Tell me about your system- PHASE 1ConnectBridge the old system to modern infrastructure.
- PHASE 2MoveData and features migrate piece by piece.
- PHASE 3RetireThe old system goes when the new one has proven itself.
↳ Stop after any phase and you’re better off than before it.
Emergency fix
Something is broken right now. I diagnose and fix it.
System audit
Architecture, performance and risk, in a clear report with priorities.
Ongoing support
Priority access, fixes and improvements. A senior engineer on call.
Custom development
Web apps, mobile apps and integrations, mostly for industrial settings.
No fluff. No slide decks.
- You show me the problemA message, a shared screen, access to the repo. Whatever works.
- I diagnose quicklyNo endless meetings. I dig in, find the root cause, tell you what’s going on.
- I fix it, or map the way outYou get a working solution, not a presentation about one.
When a project needs more than me
I bring in people I’ve worked with for years, for exactly as long as the project needs them. You still talk to me. I own the architecture and the result.
- FULL-STACK ARCHITECTS
- PENTESTERS
- FRONTEND DEVELOPERS
- MARKETING, FOR LAUNCHES
“Software that’s boring in the right ways. Clarity beats cleverness every single time.”
I’ve worked across startups, long-lived business systems, and products that had to survive real users, real traffic and real constraints. Tools are secondary. Choosing the right level of complexity is the actual job.
- EN · PT · ES · DE · EL
- US LLC · BASED IN BELGRADE
- MORE ABOUT ME →
Field notes from production
Things I ship on the side
Too many years overanalyzing ideas. Now I just ship them.
A shared record of the client websites a freelancer or small agency looks after: who controls each domain and hosting account, who handles renewals, and when a registrar, nameserver or certificate quietly changes.
Bookmarks that expire by default. Links get seven days to prove they matter.
Three daily puzzles for the Balkans, the same for everyone, every morning.
A native utility for travelers and digital nomads.
Got a problem? Send it over.
A short description is enough, or just the error message. I’ll tell you whether I can help.