[eonnen]

"It is similar to a push notification server like the iOS Apple Push Notification Service, but without the ability to store messages if the client is offline."

Not even close. Layer in X509 authentication and flaky mobile networks and now you're into tuning backoff while dealing with the CPU overhead of the TLS negotiation.

Also of note, AWS' network use to flake out at around 400K TCP connections from the public network. May no longer be the case but it certainly was ~2012.

[toast0]

FYI, there's an unpublished limit on established TCP connections, bigger instances have bigger limits. It's hard to hit them with normal applications (you'll run out of memory from the TCP buffers and application state), but you can definitely hit them if you're doing weird things.