[tomjakubowski]

CORS does not double latency for every single request. It adds the additional overhead of a separate OPTIONS request for every single request. Unless the responses are as trivial to compute/serve as OPTIONS responses are, that will be way less than a doubling in latency.

[javier2]

What I mean by latency is the transport latency, even assuming 0ms OPTIONS compute time, you still need twice the round trip time.