We use XTDB 1 and have a multi replica production instance with about 600GB of data at ~100 million transactions. The biggest problem we have is with minor versions bumping the underlying RocksDB i dex version, requiring a full reindex of the main "golden" data store taking days to weeks.

AFAIK this is not solved in XTDB 1. I'm hoping XTDB 2 provides a better upgrade path for modestly sized databases like ours.