Context
Unlike Automotriz and BR Logística — internal operations panels — Happy Pet is a self-service product. Any client can open the calendar, pick a day, see open slots and book without going through staff.
The salon was coordinating over WhatsApp. It needed real availability on screen and a hard operational rule: transfers (max 4 per day).
Frontend
A React + TypeScript SPA on Cloudflare, same UI approach as the other production systems, but a different flow: customer-facing and built for mobile.
- Client and admin access (login, sign-up and password recovery).
- Monthly calendar: past days locked, preferred day and time-slot availability.
- Booking with personal data, pet details, notes and whether a transfer is needed.
- Pet management (up to 10): weight, breed and notes; weight sets the service price.
- Own bookings list and cancellation.
The public repository is the backend; the frontend follows the same React/TS pattern as the other projects and is not linked here.
Backend
That is the distinctive part. The API (Java + Spring Boot + PostgreSQL) does not stop at application-level checks: slot availability and the transfer cap are enforced in the database, so two clients cannot take the same slot or a fifth transfer on the same day.
- Formal domain: business rules traced in tests.
- Concurrency guaranteed in PostgreSQL (not only in code).
- CI with race, mutation and e2e tests.
- Docker for a reproducible environment.
Outcome
Clients book on their own. The calendar shows real slots, and the 4-transfers-per-day cap holds even when bookings arrive at the same time.