> it's under your control to find a host that doesn't have these issues
All hosts will have these issues, the only question is how often. If you need 100% consistency, then you can't use the free Sidekiq. Personally, I've never needed Sidekiq pro (as these kinds of crashes are extremely rare). But this will depend on your scale and use case.
> And not even a full-on ACID database is going to be 100% reliable if you yank the power cord at the wrong moment
This is only true if there's bugs in the DB, or some underlying disk corruption happens. The whole point of an ACID database is that they're atomic, durable, and consistent, even in the worst case scenario. If a power failure corrupted my SQL database I would feel very betrayed by the database.