Autoscaling responsiveness is how quickly an autoscaler responds to a capacity issue. If you want to avoid slowdowns and timeouts, you want your autoscaling to be as responsive as possible.
How Quickly Does Judoscale... Scale?
The Judoscale adapter packages report metrics every 10 seconds and the autoscaling algorithm also runs every 10 seconds. This means Judoscale will send an upscale request to Heroku within 20 seconds of a queue time "breach" (queue time exceeds the threshold you've specified).
After sending the request to Heroku, it’ll take between 20 and 60 seconds (depending on the startup time for your app) for your new dyno to begin receiving requests. Note that performance, private, and shield dynos take longer to start up than standard dynos.
What if My App Struggles to Recover From a Capacity Issue?
Apps that receive steep spikes in traffic should consider scaling up by multiple dynos at a time.
Scaling up by more dynos per scale-event will help prevent traffic spikes from turning into prolonged slow-downs once the intial spike traffic is handled. Read more in Tuning Your Application.