Failover.

also: failovers · automatic failover · fail over · promote a replica

Replacing a failed primary: followers notice missed heartbeats, a new primary is promoted and clients are pointed at it.

the two-minute refresher

Detect (heartbeats time out after 10-30 s), elect a new primary, repoint connections.
Writes fail during the window (10-60 s): return errors, queue them, or make failover fast.
With async replication the newest writes may be lost on promotion.
The old primary must be fenced, or you get split brain.

also: failovers · automatic failover · fail over · promote a replica

Replacing a failed primary: followers notice missed heartbeats, a new primary is promoted and clients are pointed at it.

Detect (heartbeats time out after 10-30 s), elect a new primary, repoint connections.
Writes fail during the window (10-60 s): return errors, queue them, or make failover fast.
With async replication the newest writes may be lost on promotion.
The old primary must be fenced, or you get split brain.