I think of the Stripe Mongo install, as it was a decade or so ago. It really was sharded quite wide, and relied on all shards having multiple replicas, as to to

I think of the Stripe Mongo install, as it was a decade or so ago. It really was sharded quite wide, and relied on all shards having multiple replicas, as to tolerate cycling through them on a regular basis. It worked well enough to run as a source of truth for a financial company, but the database team wasn't small, dedicated to keeping all that machinery working well. Ultimately anyone doing things at that scale is going to run a small priesthood doing custom things to keep the persistence payer humming, regardless of what the underlying database is. I recall a project abstracting over the Mongo API, as to allow for swapping the storage layer if they ever needed to