Sample work · Software & Web Apps
Booking system: available slots, booking, cancellation, without double booking
A small appointment API with time zones, cancellation via token, and a database that does not allow two bookings for the same slot, even with concurrent requests.
Sample work (demo), not a client job. Built as a trial task with invented example data; the check figures below come from the automatic test run and are not polished.
What was built
- Available slots per resource, output in the customer's time zone
- Booking, cancellation with token, lockout period before the appointment
- Concurrent requests for the same slot: exactly one wins, the others receive a clear rejection
How it was checked
Automatic test run on 2026-10-31, taken from the log (test data invented, figures measured):
- 22/22 HTTP cases green
- all 8 invalid inputs 422
- concurrent: [201, 409, 409, 409, 409, 409, 409, 409, 409, 409, 409, 409]
- 5 active bookings in the DB, overlaps: 0
Limits
What this sample does not cover, so nobody expects more:
- one provider time zone per installation, fixed opening hours Mon-Fri (no holidays, breaks, vacation - would be configuration, not part of the sample)
- no payment gateway, no reminder emails/SMS (would require a mailing service), no calendar synchronization (Google/Outlook require customer access)
- SQLite for one server process; multiple instances require PostgreSQL (exclusion constraint)
- user interface not part of the sample - API tested via HTTP
Something like this for your business?
Describe briefly what you need. You get a fixed price before I start; nothing happens without your yes.