RentIt

Every rental moves through a 12-step flow: request, approval, payment, handover, in rental, return and completion, with disputes and cancellations built in. If two people try the same action at once, a database lock lets only one of them through.

The balance is not a single number but the sum of transaction records, and refunds are new records rather than deletions. Even if a Stripe payment is delivered twice, it is credited to the wallet only once.

A one-time code, photo/video proof from both sides and a review window protect each handover; when the window ends the system moves the flow on by itself, and an admin resolves disputes.

With PostGIS, listings are filtered and sorted by distance, combined with category and price filters.

A separate Python service combines content similarity, distance, similar users' behaviour and items rented together to produce recommendations; results are stored in the database so the API reads them fast. New users see popular nearby listings.

Renter and owner chat in real time with Socket.io, with a typing indicator and unread counter.

JWT and Google sign-in, rate limiting, input validation and ownership checks on every endpoint. I wrote more than 100 automated tests with Jest and Supertest.