Instead of hourly polling, which I find quite inelegant, couldn't you trigger creation of new schedule rule with the correct time that then triggers the publishing?
In theory yes. I could provision a new function with an exact cron schedule to run once and then tear itself down.
In practice, this is a lot of extra logic to write to achieve this and would also potentially make own AWS account rather messy.
The hourly cron runs about 720 times a month which is far below the 1,000,000 free invocations that lambda provides under their free tier.
1. fire off AWS Step function on new post to S3 bucket
2. read delay / schedule time in metadata from (assumable) markdown post
3. trigger AWS Step Function using the Wait State defined based on read value from 2.
4. As part of Step Function: After Wait State -> Execute Lambda to publish post.
Note: 3) requires setting variable time in Wait State based on environment. Haven't read up so don't know if that's possible, but guess it should be.
This looks like a great alternative solution!
Haven't messed around with step functions yet but was looking into it today after I found this https://www.youtube.com/watch?v=9MKL5Jr2zZ4&t=226s
Are you using step functions for other flows?