Even if customers are only running one instance, I would expect the whole thing to rebalance in an automated way especially with fly.io being so container centric.
It also sounds like this is some managed Postgres service rather than users running only one instance of their container, so it’s even more reasonable to expect resilience to host failure?
I believe the underlying reason that precludes failing over to a different host machine, is that fly volumes are slices of host-attached nvme drives. If the host goes down, these can't be migrated. I _think_ instances without attached volumes will fail-over to a different host.
Of course, that's not ideal, and maybe their CLI should also warn about this loudly when creating the cluster.
And +1 to the sibling comment; Fly makes it very clear that single instance postgres isn't HA, and talks about what you need to do architecturally to maintain uptime.
edit: Remove triple as not certain about level of redundancy
>Amazon EBS volumes are designed to be highly available, reliable, and durable. At no additional charge to you, Amazon EBS volume data is replicated across multiple servers in an Availability Zone to prevent the loss of data from the failure of any single component. For more details, see the Amazon EBS Service Level Agreement.
https://aws.amazon.com/ebs/features/#Amazon_EBS_availability...
If a read replica fails, I'd expect no downtime (possibly a few errors as connections get cut off abruptly). Although there's always the risk that the remaining instances aren't able to handle the additional load.
If the master fails, you'll get a ~2min downtime
Down time is one thing. Data loss is something else.
Depends on where in your development cycle you are. If you just got started and haven't even figured out what you're actually building (prototyping), you shouldn't really use a hosting provider that randomly lose instances.
If you're on the other hand have done everything to improve your applications performance, had to resolve through-output issues with a distributed architecture and now running 10+ instances, then losing one host shouldn't impact you too much. But you really shouldn't start this way, it's doing web services the hard way and introduces a lot of complexity you shouldn't want to deal with when you're still trying to find product market fit.