In a database with single-leader replication, all nodes need to agree on which node is the leader. The leadership position might become contested if some nodes can’t communicate with others due to a network fault. In this case, consensus is important to avoid a bad failover, resulting in a split brain situation in which two nodes both believe themselves to be the leader (see “Handling Node Outages”). If there were two leaders, they would both accept writes and their data would diverge, leading to inconsistency and data loss.
