The best document store is probably either a filesystem or S3.
Use a relational database. Postgres or MySQL. MySQL used to be heinous 20 years ago, but it's alright now. That's about how long these things take.
The primary thing you want from your data storage layer is you want it to be boring. You want all of the foot-shooting to have happened to other people and to be painstakingly documented. This is what relational databases give you. Are they the most ideal thing in the world always? Heck no. Are they extremely well-understood, operationally and in terms of the performance envelope? Compared to everything else, yes.
When in doubt, do the boring thing.
If your data storage layer is interesting, you're a database company and you know to ignore me. Otherwise why are you spending complexity budget on something which isn't the problem you're actually trying to solve?
Use a relational database. Postgres or MySQL. MySQL used to be heinous 20 years ago, but it's alright now. That's about how long these things take.
The primary thing you want from your data storage layer is you want it to be boring. You want all of the foot-shooting to have happened to other people and to be painstakingly documented. This is what relational databases give you. Are they the most ideal thing in the world always? Heck no. Are they extremely well-understood, operationally and in terms of the performance envelope? Compared to everything else, yes.
When in doubt, do the boring thing.
If your data storage layer is interesting, you're a database company and you know to ignore me. Otherwise why are you spending complexity budget on something which isn't the problem you're actually trying to solve?