> They can happen, yes, although this should be a rather rare event

For our use case, it didn't matter if it was rare or not: the fact that it could happen at all meant we needed to be robust to it, which basically meant storing the entire database in memory.

> We added support for exposing this via the `source.sequence` field a while back upon request by the Materialize team btw.

Yes, I helped work on this! I'm not sure whether Materialize is still using it (it's been years since I've thought about MZ/Debezium integration) but it was helpful, thanks.