Yes, in that case you can lose committed data. The normal way to avoid that is to use synchronous replication. That is easy to set up, but has some implications:
- it will slow down data modifications considerably - you should have a low network latency between the machines - the whole system becomes unavailable if the standby goes down, so have at least two synchronous standbys if you want good availability
Thanking all for the prompt replies and guidance for clarifying the doubts and queries.