I remember hearing something like Google Global Cache proxies requests to Google datacenters so that retransmit times, due to last mile issues, are lower since

I remember hearing something like Google Global Cache proxies requests to Google datacenters so that retransmit times, due to last mile issues, are lower since packets do not need to travel all the way to the datacenter. My guess is that they might do HTTP TLS termination there, and when the backend failed to respond in time returned 502.