No, it's connections/server, unless the provider has separate back-end IPs for each user (not a bad idea, but I'll bet they're not doing that).
The tuple consists of the source IP, destination IP, source port, and destination port. The first, second, and last are, in a naive implementation, potentially universal to all applications/instances/sessions on the server, so your number space is reduced to the ~60k source ports.
This is an incredibly easy problem to solve, but it does need a small bit of attention by PaaS providers to ensure they're not going to hit it.
I am confused as to how the source IP can be the same for every connection, as even the naivest socket server will be accepting connections from many different users, each with their own source IP, which makes this 60kconns/port/user.
You and several other people are completely failing to read and comprehend the blog post in its entirety. This has nothing whatsoever to do with where USERS are connecting from.
If you have X sessions on a single front-end server opening one or more individual connections to a single back-end server (e.g. CouchDB), at least X ephemeral ports are used on the front-end server to connect to the back-end server. As X increases, you can reach a point where you have a serious problem. If X gets anywhere near ~60k, it's game over.
The tuple consists of the source IP, destination IP, source port, and destination port. The first, second, and last are, in a naive implementation, potentially universal to all applications/instances/sessions on the server, so your number space is reduced to the ~60k source ports.
This is an incredibly easy problem to solve, but it does need a small bit of attention by PaaS providers to ensure they're not going to hit it.