Meaning
Being available outside regular business hours to respond immediately to critical production alerts or system outages.
Three examples from work
Shift handover
Dev 1Who is on-call for the payment microservice this weekend?
Dev 2I am on-call until Monday morning. All alerts are routed to PagerDuty.
Incident response
LeadWere you paged while on-call last night?
DevYes, a database replica failed over, but the failover was automatic.
Policy sync
DevOpsWe updated our on-call runbook with new incident response playbooks.
DevGreat, clear steps make night shifts much less stressful.
Usually used as 'be on-call' or 'on-call rotation'. Engineers on-call carry a phone or laptop ready to triage high-severity production alerts.