Glossary for high-availability and production engineering

A SPOF is one part of a system that can take the whole service down when it fails.

Fencing is the act of cutting a broken or uncertain node off before another node takes over its work.

STONITH is a blunt cluster safety mechanism that powers off or isolates a suspect node.

Split-brain happens when parts of a system lose contact and more than one side thinks it is in charge.

Quorum is the rule that says a cluster may act only when enough trusted members agree.

Failover is moving service from a failed or unhealthy component to a prepared replacement.

Load shedding is intentionally refusing or delaying lower-value work so the important path stays usable.

A recording rule saves the result of a metrics query so dashboards and alerts can read it cheaply later.