Case study
Likewatt
Sept. 2024 → present
SaaS vendor in renewable energy. Interface redesign, Firebase → MongoDB migration and split into microservices: load times cut in half for more than 2,000 professional users.
01
Context
Likewatt is a SaaS vendor in renewable energy, based in Villeurbanne, France. Its users are professionals, including teams at TotalEnergies, Crédit Agricole and Eiffage.
I work there as a full-stack developer: as a work-study student from September 2024 to November 2025, then full-time since November 2025.
02
Problem
A legacy application written with React class components, with an outdated interface.
Recurring bugs and slow load times for users.
A Firebase database and a monolithic architecture that needed to evolve.
03
What I did
- Migration of the legacy application (React class components) to React 18, TanStack Router and TanStack Query.
- Redesign of the interface and user experience, from mockups to implementation.
- Database migration from Firebase to MongoDB.
- Split of the application into microservices.
- Performance optimization.
- New feature development and software maintenance.
04
Result
Load times cut in half for more than 2,000 professional users, including teams at TotalEnergies, Crédit Agricole and Eiffage.
Far fewer bugs, on a modernized codebase the team can evolve more easily.
05
Stack
- React
- TypeScript
- TanStack
- Zustand
- Tailwind
- NestJS
- MongoDB
- PostgreSQL
- Docker