What is lizard?

Lizard is an infrastructure-as-code project for AWS that acts as a spending circuit breaker. It watches your AWS billing through CloudWatch Alarms, and when your estimated charges cross a threshold you set, it automatically stops EC2 instances that you have tagged as expendable, so a billing spike does not keep growing unattended. The idea came from a real AWS billing bug on July 17, 2026 that showed some accounts estimated charges in the billions of dollars. Lizard was built so people could have a safety net running in the background: if spend crosses a line, the resources marked as stoppable get shut down. The readme is upfront about what this tool can and cannot do. It cannot figure out which specific instance is causing a cost spike, because a billing alarm only reports that spending went over a limit, not which resource caused it. Instead, you tag the instances you are willing to sacrifice with a specific tag, and when the alarm fires, every instance carrying that tag gets stopped, not just the one responsible for the extra cost. Instances are stopped rather than deleted, and the permission to stop them is enforced through AWS identity and access management rules, not just through the automation script, so an untagged instance cannot be stopped even if something in the automation goes wrong. Setting it up requires knowing that AWS billing metrics are only available in the us-east-1 region, and that the payer account must have billing alerts enabled before Lizard can see spending data at all. The project uses Terraform for its infrastructure code and Yarn plus a tool called lefthook for contributor tooling, and it is currently a small, early project with a single author.