I build modern web apps with React, Next.js and TypeScript, and ship them full-stack with Prisma, PostgreSQL and Supabase — clean, typed and tested, from the database all the way to production on Vercel.
Frontend
Backend & Data
Testing & Tooling
🏋️ Workout Tracker — Full-stack fitness app
Next.js 16 · TypeScript · Prisma + PostgreSQL (Supabase) · Clerk · Zod · Vitest + CI
Authenticated users create, edit and delete workouts and exercises through Server
Actions, with per-user ownership checks on every mutation, Zod-validated input, a
Vitest test suite and a GitHub Actions pipeline that runs on every push.
→ Live demo
⚽ Sport App — League & team browser
Next.js 16 · TypeScript · Tailwind CSS · TheSportsDB API
Browse football leagues and teams with instant search, dynamic routing and cached
(ISR) data fetching, plus proper loading / error / not-found states.
→ Live demo
🍸 Cocktail Browser — React SPA
React 19 · TypeScript · React Router — search, pagination and a favourites system over an external API.
💸 Mini Budget Tracker — React + TypeScript
Income & expense tracking with a running balance, categories and a clean transaction history.
🌐 See every project live on my portfolio → mikolajmichalak.dev
- Full-stack architecture — designing data models, server actions and auth flows end-to-end
- Databases & data modelling — relations, migrations and type-safe queries with Prisma & PostgreSQL
- Testing & CI — meaningful tests with Vitest + RTL, verified on every push with GitHub Actions
- Web performance — Core Web Vitals, caching and measuring real production apps
- Portfolio: mikolajmichalak.dev
- LinkedIn: linkedin.com/in/mikolaj-michalak
- Email: mikolaj.michalak.dev@gmail.com