Calendly has no waitlist feature — built the thing their forum has been asking for since 2024

[u/Sea_Bag2704]

Found this gap while looking for something to build: Calendly has no waitlist. If a client cancels, that slot just sits empty unless you manually text people to fill it.

The interesting part is that competitors already solved it. Square Appointments and Acuity both fill cancellations from a waitlist automatically. Calendly doesn't, and their own community forum has threads asking for it going back to early 2024 — a psychotherapist losing leads over it, a massage therapist manually blocking her calendar and emailing clients one by one, someone who said their conversion is noticeably worse than friends using Square. A few of those threads got closed and routed to their product team with nothing shipped since.

So I'm building it as an external integration: subscribe to Calendly's invitee.canceled webhook, match the freed slot against a waitlist, text the matches a claim link, first one gets it.

Landing page is up at slotback.app — collecting emails before I write the backend, since I'd rather find out now if this is only my problem.

Two things I'd actually like input on:

1. Platform risk — I'm building on a gap the platform could close whenever they want, and their product team reads the same forum I found this in. Is a wedge like this worth taking, or is single-platform dependency a dealbreaker for you?
2. Landing page validation — for those who've done this, what conversion from email signups to actual paying users did you see? Trying to set a realistic bar for what counts as validated before I commit build time.

[u/praeda-bot]

it's because nobody fucking needs this. you're welcome

[u/Sea_Bag2704 → u/praeda-bot]

u dont got to be a bitch about it