Bookly
A real-time booking and scheduling platform for businesses that take appointments.
Double bookings cost businesses money and customers. We built a booking platform where two people can click the same slot at the same moment and exactly one of them gets it.
The challenge
- 01
Two customers click the same free slot at the same moment — the classic race that double-books a calendar.
- 02
Held slots that are never confirmed block everyone else.
- 03
Customers and businesses in different time zones and languages must see the same calendar correctly.
- 04
Every open calendar has to stay current without anyone refreshing the page.
What we built
Three layers against double booking
A row lock, a database constraint and safe retries. In tests, 15 simultaneous raw database connections race for one slot: exactly one booking survives.
Holds and waitlists
A slot is held for 10 minutes while the customer confirms, then released automatically. Freed slots go first to whoever waited longest.
Live in every tab
When a booking changes, every open calendar updates within a second — no refresh.
Four languages, every time zone
English, Turkish, Russian and Azerbaijani with correct plurals; every time is shown in the viewer’s own zone, and emails arrive in each person’s language.
Tech & SEO notes
- Next.js, TypeScript, PostgreSQL and Prisma; live updates via PostgreSQL notifications and server-sent events.
- Integration tests run against a real database, including the concurrency stampede under two isolation levels.
- Calendar export (.ics), email notifications and one-command Docker deployment.
Want this for your business?
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