Booking kit: stop double-booking with range exclusions and live slots

UpdatedSeptember 19, 2026

Double-booking is not a UI bug. It is a write-time integrity failure: two clients confirm the same provider window, both see a green check, and your calendar lies. A booking product you own should reject the second insert in the database, then refresh open slots for everyone still looking.

This post is the how-to for that spine on OTF's Booking kit (Cadence). It is not the ownership tour at /blog/booking-kit-own-the-repo, not the greenfield path at /blog/how-to-build-a-booking-system-with-ai, and not the compare at /blog/otf-vs-cal-calendly-booking. If your buyer question is "how do overlapping appointments get blocked when two phones hit Pay at once?", stay here.

This is an excerpt. Read the full post at otf-kit.dev/blog/booking-kit-no-double-booking — full-stack kits your AI coding agent can actually ship to production. Browse the kits →

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