"We need to add a new environment variable to all prod servers. Right now." A message from the development team lead. 150 EC2 instances, all tagged with Environment=prod. SSH into each one individually? Impossible schedule. This is when an operator reaches for Run Command. Define the command, specify targets by tag, set concurrency and error limits, press execute—and it's deployed to all 150 simultaneously. Results automatically save to S3 and CloudWatch Logs; failed instances auto-generate as OpsItems in OpsCenter.