What Happens If I Exceed the CPU Limit?

A common question we hear on Support is “What happens if our Gigalixir app(s) goes over the CPU limit?”

Unlike memory, exceeding your CPU limit does not usually result in your app being killed or restarted. Instead, Kubernetes will throttle your CPU usage.

CPU Throttling

When your app attempts to use more CPU cycles than your replica size allows, the system restricts the available processing power to keep it within the limit. To your users, this looks like increased latency or "sluggish" performance, as requests take longer to process.

If your app has a sudden spike in CPU usage but recedes within a few minutes, you may notice a temporary dip in performance, but the app will remain healthy and continue running.

Debugging CPU Issues

If you notice your app is consistently slow or you see "CPU Throttling" metrics in your dashboard, check your application logs and performance monitoring tools. Typical reasons include expensive computations, unoptimized database queries, or sudden spikes in concurrent traffic.

Prevention & Mitigation

If your CPU usage is regularly hitting the ceiling, we suggest you scale your replica size or increase the number of replicas to handle the load. This ensures your app remains responsive during peak times.

If you are having trouble debugging performance issues, you can always contact us at Support.