Ask HN: Serverless” key value store with transactions?

I am looking for a key value store that is: - based on LSM trees (hence sorted keys on disk) - Is serverless (like SQlite) - Also supports transactions

Some that I know are LevelDB, pebble, rocksDB, foundationsDB but each of them either is not "serverless" or doesn't support transactions.

What other options are out there if any? Also, how hard it would be to add transaction support to something like pebble? What particular knowledge would be required?