I build fast.
I fix what others
won't touch.
I'm Sebastian Kasiński, a freelance senior software engineer based in Opole, Poland.
8 years of experience, 6+ in mobile. I ship MVPs in days, rescue broken apps, and bring AI-powered speed to every project.
Services
Mobile Development
React Native specialist with 6+ years of cross-platform experience. Thanks to a shared codebase, I deliver iOS & Android simultaneously. Faster and cheaper than two separate projects.
MVP & Rapid Builds
I use AI tools (Cursor, Claude Code, n8n) to build functional products in days, not months. Enough to demo, pitch, or launch — without cutting corners that matter.
App Rescue & Brownfield
The codebase your whole team is afraid to look at? I diagnose the problem, fix what's broken and leave everything in better shape.
Consulting & Architecture
Code audits, architecture reviews, tech lead on demand. I help teams make the right technical decisions, and sometimes, implement them too.
Need a full team? When a project calls for it, I collaborate with trusted designers and senior engineers from my network — so you get the right people, not just one pair of hands.
How I move fast
Cursor + Claude Code
AI-native coding environment. Write, review, and refactor at 3× the speed of a traditional setup.
Codex / GitHub Copilot
Intelligent autocomplete and generation across the full stack — from boilerplate to complex logic.
n8n Automation
For simple integrations and workflows, n8n replaces weeks of custom backend code with hours of visual automation.
Process
Free consultation
Up to 1 hour to understand your problem, goals, and constraints. Free, no commitment.
Proposal
Clear scope, deliverables, timeline, and fixed or hourly pricing. No surprises.
Execution
Async work with regular updates. You stay informed without micromanaging.
Handoff
Clean code, docs, and knowledge transfer. Your team owns it from here.
Let's work together
First hour of consultation is on me — tell me what you're building.