Hey!

I’m Fedor Kosolapov — a backend software developer based in Kragujevac, Serbia. Online I go by Teddy Coder, or just Ted for short.

I write Ruby for a living: marketplaces, billing and payments, state machines, background jobs — the kind of backend code where the bug report says “sometimes it charges twice” and you spend a week understanding why.

I work in two directions:

• B2B contract development — backend engineering for clients who need correctness where money is on the line. What I offer →
• My own SaaS — M365 License Leak Detector, a tool that helps MSPs find wasted Microsoft 365 / NCE license spend (currently in development).

You’ll also find a blog with notes from the trenches, and you can get in touch about work.

This site is operated by Fedor Kosolapov PR Kragujevac, a sole proprietorship registered in Serbia. See the Legal / Company Information page for full details.