Lead AI Product Engineer · Kraków, Poland
Full-stack engineer in Kraków with 13 years in production software. For the last three years I have been the lead engineer at LIVEDAB in Germany, and on my own I built and run mosfoto.com. I work across the whole system on TypeScript, React, Next.js, Node.js, PostgreSQL and AWS.
13 yrs
In production software
5,358
Commits as Lead Engineer at LIVEDAB
211
Paying customers on mosfoto.com (Oct 2026)
3,658 hrs
Across long-term Upwork contracts (100% JSS)
Multi-tenant AI photo and video SaaS reaching 30–60% visitor adoption at German trade fairs. Own architecture and delivery across AI media generation, team permissions, CRM and GDPR on Next.js, AWS and Remotion.
Profitable solo SaaS that turns phone photos into compliant 684×883 biometric residence-card photos. 8,537 photos prepared across four languages using Next.js, Replicate face parsing, deterministic framing and Stripe.
One CLI command renders a personalized 1080p sales video for any company. Captures the live site in Playwright, scripts and voices a localized call with Claude and ElevenLabs v3, and composes the MP4 in Remotion.
Collaborative trip planner where groups save ideas from any link into a shared itinerary and vote on them. Led development at Ovdal ApS on Angular, NgRx and Symfony, with Puppeteer for link previews. Still live.
Took a German employee-survey SaaS homepage from 49 to 86 on mobile PageSpeed after its move to Hugo on CloudCannon. Measured before release: Largest Contentful Paint down from 7.1 s to 3.2 s and page transfer from 1.2 MB to 509 KB. Lazy-loaded images, split scripts, and held third-party scripts, 63 of 106 requests, until cookie consent.
Notes on shipping reliable software and working with AI coding tools.
Durable workflows over fragile chains. External model APIs time out and mobile tabs close. I build long-running AI jobs as resumable server workflows where every step falls back to its input if a provider fails.
Tests define correctness, not the coding agent. I use Claude Code daily behind a closed TDD loop: requirements become failing Playwright or Jest tests first, typed schemas set the boundaries, and code merges only when green.
Evolve in place and own the whole system. I prefer improving an existing production codebase step by step over pushing for a rewrite, and I document every handover so nobody is left guessing.
“I've worked with a lot of freelancers on Upwork, and most of those contracts end pretty quickly. Sviatoslav is one of the few I kept on for close to a year, which tells you most of what you need to know. When one of the tile generation scripts started racking up serious cloud costs, he found the cause and fixed it. Later he built a map rendering API that our AI team plugged straight into their agents. He also put real thought into working with AI coding tools, setting up rules and structure in the codebase so the generated code actually fit. When he handed his work over, he documented every step so nobody was left guessing.”
“Sviat was a pleasure to work with - professional, reliable, and incredibly fast without compromising quality. I'd gladly hire him again.”
“One of the best freelancers I've worked with on Upwork. Highly skilled, reliable, always responds quickly, and you can always count on him to deliver high-quality work.”
