It got a lot better in the ~7 series IIRC when they added checksums to the on-disk files. I don't know if you still have to recover corruptions by hand, or whe

It got a lot better in the ~7 series IIRC when they added checksums to the on-disk files. I don't know if you still have to recover corruptions by hand, or whether the correct file gets copied in from a replica. The replication protocols and leader election were IMO not battle-hardened or likely to pass Aphyr-style testing. It was pretty easy to get into a state where the source of truth was unclear. Source: Ran an Elasticsearch hosting company in the 2010's. A little out of the loop, but not sure much has changed.