Portfolio

Selected projects and products

11 projects

9 case studies

5 years experience

Dental Scheduling SaaS — multi-tenant booking that can't double-book

Multi-tenant dental booking core: strict RLS tenant isolation, atomic double-booking prevention via a Postgres partial index, live availability (Broadcast), and reserve-before-Stripe payments with an idempotent webhook. Verified 9/9 end-to-end against production. Live demo + open source.

Next.js 14 TypeScript Supabase PostgreSQL RLS Stripe

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Case Study

Legacy Rescue — abandoned 8-year-old backend

Modernization of an abandoned internal system for a multi-location retail business. Java Spring Boot backend rewritten to Node.js while keeping the React 15 frontend untouched. 21 contract items delivered 100%, zero-downtime database migration, own auth (bcrypt + JWT), HTTPS via Caddy.

Node.js Express MySQL React 15 JWT bcrypt Caddy

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Case Study

Production migration — unsupported server → reliable cloud

Migrating a live company system off an outdated server (end-of-life Ubuntu, no HTTPS, no backups) onto cloud infrastructure. 14-minute weekend cutover, HTTPS via Caddy, daily off-site backup in a second country with a verified restore, one week of supervision.

Hetzner Cloud Ubuntu 24.04 Caddy Let's Encrypt Docker rclone PM2

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Case Study

DRM Video Player — streaming platform rebuild

Web video player rebuild for a hybrid live/VOD streaming platform. Standalone module decoupled from CMS updates. HLS + MPEG-DASH, multi-audio, subtitles, watermark, full cross-browser matrix. End-to-end DRM pipeline (Widevine, PlayReady, FairPlay) via a KMS-agnostic license proxy.

HLS MPEG-DASH MSE EME Widevine PlayReady FairPlay

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Case Study

Lead Generator — AI pipeline for buying signals

3-phase system analyzing OLX job postings: rule-based pre-filter eliminates 70% of noise, Claude Haiku scores automation potential and trigger score, Sonnet drafts personalized outreach. 100 postings in 2 minutes for under $0.30.

Python Claude AI Haiku Sonnet Jinja2 HTTP API

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Case Study

AI Consultation System — two-tier funnel

Two-tier AI consultation system: free qualification (Claude Haiku) + premium technical analysis for 200 PLN (Claude Opus). Stripe, Supabase, Resend integration. Context continuity between sessions, JSON summaries, transactional emails.

Astro Claude AI Stripe Supabase Resend TypeScript

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Case Study

Studio Manager — System Rescue

Fixed critical bugs in a no-code platform: payment vulnerability (multiple withdrawals), Telegram webhook limits (external microservice on Deno Deploy), OAuth security gap (3-tier RBAC), tax logic errors.

Supabase Deno OAuth RBAC Telegram API

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Case Study

Studio Manager — when fixing one bug surfaces eleven more

A compliance email bug surfaced three layers of hidden data quality issues: 11 historical records (client knew of 4), 2 platform bugs, a fundamental UX trap in the panel (empty field rendered as "no"). 5 promised items + 50% discovery scope.

Base44 Deno Deploy Webhooks Resend Compliance

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Case Study

Payout engine — silent failures fixed at scale

A browser-side payout flow silently half-completed an 18,080 CHF / 212-record run. Rebuilt with bulk operations (~272 HTTP calls → ~10), a payout state machine, nightly audit + Telegram alerts and one-click recovery. 210 records: ~126s (failing) → 3.9s.

Base44 Deno TypeScript React Telegram API

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Product

Educational Platform

Custom platform for learning programming and mathematics. Interactive courses, Code Playground (online compiler), 2D/3D function calculator, C++ pointer visualizer.

Astro React TypeScript Supabase PostgreSQL

Product (WIP)

Tutor Manager

SaaS for tutoring management — scheduling, billing, materials, student communication. Under development.

Next.js Supabase TypeScript Stripe

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