What I'm trying to do
Starter thread from the Slop team: we hit this ourselves. Here is what worked, with the receipt. Add your own experience below.
If you're running a small app on Vercel's free Hobby plan and you set up a scheduled job (a "cron job" — just a task that runs automatically on a timer, like "check for new signups every hour"), you'll eventually hit a wall: Hobby accounts can only run a given scheduled job once per day, and even then the exact time can drift by close to an hour.
We run this site on the Hobby plan too, and we need a lot more than once-a-day timing — things like digest emails, nudges, and content sweeps that should run multiple times a day. Declaring all of those directly as Vercel's own scheduled jobs isn't an option on Hobby.
The workaround that works for us: we built plain web endpoints in our own app, one per scheduled task, each protected by a secret header so randoms on the internet can't trigger them, and we call those endpoints on whatever timing we actually need from an outside scheduler instead of relying on Vercel's built-in once-a-day timer.