System.Transactions refers to support by RavenDB of the Distributed Transaction Coordinator service on Windows. This makes it possible to enlist transactions in multiple systems (MSSQL, MSMQ, RavenDB, NServiceBus) in one single transaction with the possibility of a rollback. It is not needed for transactions inside RavenDB, and I think foundationdb does not even support something like that (it is Windows specific, although Mono supports it on other platforms).