Can I make Loadster exclude error responses when calculating response times?

Sure! There’s a global setting to do exactly this.

Go to the Settings page of your dashboard. In the Playback Options, you’ll see an option called Include error responses in response times.

This option is checked by default, meaning that error responses (at least HTTP 4xx/5xx and validation errors) are included in the response time metrics (average response times, maximum/minimum response times, and percentiles).

If you uncheck it, only successful responses with an HTTP 2xx/3xx status code and no validation errors will be included in these metrics.

In most cases you’ll likely want to avoid errors in your load test anyway.