How do you schedule your lambda invocations?

We have rolled our own solution in AWS for triggering lambda functions in the future with a DDB table that has a key structure

pk - YYYY-MM-DD

sk - full timestamp representing time after which this event should be triggered

and another lambda that queries this table for all unprocessed events before Now and pushing them to a SNS topic that triggers the relevant lambda handler based on a messageId.

This feels pretty hacky and has been something I have been thinking about a lot lately. When you cant use cron (or some other in-memory based solution) how have you scheduled code to run at a specific time in the future?