Platform migration to React & NestJS
Rewrote the o5.Food core from PHP/jQuery to TypeScript/React/NestJS. Modular architecture, typed API, 500+ business clients migrated with zero downtime.
Challenge
o5.Food served 500+ restaurants across Russia, but the codebase was a PHP/jQuery monolith that grew from an MVP. No tests, new features took 3-4 weeks to ship, and onboarding new developers was painful. It needed a rewrite, but without taking production down.
Technical details
Solution
I went with the strangler fig pattern - old and new systems running side by side, Nginx routing between them. Each sprint I took one module, rewrote it in React + NestJS, and covered it with tests. Extracted the API into a standalone NestJS service with full typing and auto-generated Swagger. On the frontend - React Query for server state, custom hooks for reusable logic. Set up CI/CD via GitLab - linting, tests, deploy on merge.
Result
Migrated all 500+ clients over 8 months with zero downtime. Feature development speed increased 3x, test coverage reached 70%. Deploy went from 40 minutes of manual work to an automated 5-minute pipeline.