Optimal executors for large concurrent builds

Looking for recommendations on support high number of concurrent builds 100 parallel builds per seconds.
Which kind of executors works best for us.
I believe there are 3 main options for us

  1. Shell (EC2-instance in autoscaling)
  2. Docker (Auto-scale)
  3. Kubernetes.

We have tried the kubernetes executors but they are slow. Apart from the usual time for creating a pod, s3 cache etc, the usual build time is also high when comparing to running build in a t2.small machine(Pod is created with equivalent cpu and memory spec).

But then ec2-autoscaling is slowest of all.

What is a recommended executors on achieving high build throughput.