@cliftonlabrum Can you elaborate on the tests that you made?
I was able to get +/-4200 concurrent connections for 1 minute with a total of about 250k requests and an 89ms avg response time. Anything beyond the 4200 connections would choke the servers with timeouts.
This was an optimized build with Swift 3 and Ubuntu 16.04 (no database involved). The requests were plain simple HTTP GET with no Message Body. Memory pressure wasn't an issue, but again, no database whatsoever.
My guess is, you won't be able to reach 10.000K concurrent connections with Digital Ocean on a cheap 1x 1.7GHz CPU instance, ROS or no ROS.
I also wonder if this would still be true with more cores added to the instance, since ROS is single threaded? @ianward could you elaborate and give us your insight on this also?