[shalabhc]

Getting the message to the right container is one bottleneck. Currently this is routed through a couple of hops and includes some polling. This could all be optimized (if we had a direct line to the container) but the same messaging model is used in other contexts and would need architectural changes. Another bottleneck is running `source.pex` itself takes a few seconds to start up because it analyzes user code (and in some cases may do expensive computation.) But you're right: if `source.pex` as a hello world program, just downloading and running it should be pretty fast - I'd expect around 1s.