[feike]

> Can Patroni tell if master node is not responsive because it is busy vs dead

No. But the contract Patroni has is this:

I only serve a master (primary) if I have the lock. If I do not have the lock I will demote.

This results in that there can be only 1 primary active at any given point in time, even if the network is partitioned.

This in and of itself does not guarantee no-split-brain situations, a split-brain can occur if writes were made on the former primary, but not yet on the future primary. This however can be mitigated with synchronous replication.