Sounds like something you could do with SQS and Lambda. They just have massive datacenter infra and compute at disposal.
But in reality, any managed queue or even a well structured DB table can be fine, depending on your scale.
I remember this being an issue a long time ago, where Lambda pretty much was a non starter for use cases where you're running 1000 independent tasks that each, on their own, is a small unit of work (just 1 or 2 database queries).
Long way of asking: is there a way to share a database connection between lambda functions or does each run need to re-establish / re-authenticate a new connection with the database?
https://www.jeremydaly.com/reuse-database-connections-aws-la...
It will get re-used across lambda invocations as long as the instance of it isn't killed which typically happens after a few minutes
This outlines creating the handler outside the function context to allow the client to be reused between invocations.