Failover
ELI5 - The Vibe Check
Failover is what happens when your primary database keels over and, instead of the whole app going down with it, a standby replica gets promoted to take its place automatically. It's the database equivalent of a backup quarterback getting shoved onto the field mid-game because the starter just got hurt, ideally the fans barely notice.
Real Talk
Failover is the automated or manual process of switching from a failed primary database to a standby replica, which is promoted to become the new primary. Automatic failover systems, like Patroni for Postgres or managed cloud offerings, detect primary failure via health checks and handle replica promotion and client redirection, minimizing downtime.
When You'll Hear This
"The failover kicked in and we lost about four seconds of writes." / "Test your failover procedure before you actually need it in production."
Related Terms
Load Balancer
A load balancer is like a traffic cop for servers.
Logical Replication
Physical replication copies a database byte for byte, same version, same everything.
Read Replica
A read replica is a copy of your database that only handles read queries.
Write-Ahead Log
The Write-Ahead Log (WAL) is the database's diary. Before changing any actual data, the database first writes what it's about to do in this log.