Incident Overview
A small platform team runs a web application behind an Application Load Balancer (ALB) with a target group of three instances. During a tidy-up, an engineer edits the target group health check: the path changes from / to /healthz, the port changes from traffic port to an override value, and the success codes are set to 200.
Within minutes, users report intermittent 502 responses and the console shows targets as unhealthy.Your task is to decide the safest first action. The incident is rated SEV-2 for the fictional impact: most requests fail, but the application processes are running.
Investigation Options
Review the available operational moves and select the best immediate action.
Restart all three instances immediately
Record current settings, then revert the health check to the last known good path and port
Open the instance security group to all traffic to test
Raise the idle timeout on the load balancer