@starsend I have just spend way too much time (and now it turns out money as well) on MongoDb Atlas (AWS hosted). Others have done DocumentDB. You could also cluster it or run if off an instance (but those non-managed services have to have persistence managed too). So,iIt depends on your budget. I found the dev version on docker seamless, but productionising is harder and expensive (in AWS).
It seems you need to think about ownership of data (self hosting because I don't see export functionality), cost (in small scale I would run with Novu—or a low availability self-hosted version).
From what I am seeing between setup instructions and data migrations, you are going to have to work harder than expected. For example, you need to setup redis and s3 in some form too—plus logging. Also, when containerising there are at least 4 workloads to setup—as well as the front door, etc.
I plan to share my terraform scripts to help people understand the scope of this exercise and that Novu's pricing is reasonable particularly when you take into account the maintenance costs.
I hope this is a reasonable assessment and helpful.