What Is a Pod Disruption Budget?
A pod disruption budget (PDB) is a Kubernetes policy that caps the number of pods from a workload that can be voluntarily evicted at the same time. It is enforced during operations like node drains, cluster upgrades, and autoscaler scale-downs. The budget keeps a minimum number of replicas available so the service stays healthy while nodes are recycled.
Why it matters
Without a PDB, a routine node drain could evict every replica of a service at once and cause an outage. A budget forces voluntary disruptions to proceed gradually, preserving capacity throughout maintenance.