[octo888]

3000 pps / 6 Mbps is pretty much nothing for that server. I wouldn't change random network sysctl options.

> This suggests to me that the bottleneck isn’t CPU or app logic, but something deeper in the stack

Just a word of caution - I have seen plenty of people speed towards eg "it must be a bug in the kernel" when 98% of the time it is the app or some config.

[hnroo99]

Yeah changing the sysctl options was a shot in the dark... I really hope it's my app code. But the fact that the same bottleneck occurs even when I add more containers which decreases the load per container confuses me. I mentioned this in another comment but I wonder if socket.io broadcast calls share the same I/O resource or something. Maybe a lock?