When scaling from 0 to 1 instances, yes, you have to wait 19 seconds.
For scaling N --> N+1 - If you configure the correct concurrency value (the number of parallel requests one instance can handle), Cloud Run will scale up to additional instances when getting to X% (I think it's 70%). That will be before the instance is fully exhausted.
So your users should not experience the 19 seconds cold start.
For scaling N --> N+1 - If you configure the correct concurrency value (the number of parallel requests one instance can handle), Cloud Run will scale up to additional instances when getting to X% (I think it's 70%). That will be before the instance is fully exhausted. So your users should not experience the 19 seconds cold start.