I love this. This is a property already baked into another messaging queuing system called Pulsar and I've thought about writing my own for internal use (maybe to be open-sourced). The only quirk that I see is this link in the project description readme:

> it is guaranteed that each message will be saved in exactly one S3 file

This can get expensive. Specifically a 1-to-1 write per message with S3 (or any cloud storage provider) gets expensive very, very quickly. Further, when reading from cloud storage, you've got to read one message (object) at a time which adds up as well. I'm not talking about egress bandwidth either, I'm talking about S3 PUT/GET operations. I'd love to see some kind of batching operation that takes groups of messages (perhaps configurable time/size limits?) and writes them as a blog to cloud storage.