With a single ejabberd node, what factors limit the number of possible simultaneous users it can support?
The scenario I'm thinking of is this: Many users on the node, all in the same domain. These users don't communicate with each other, only with users in other domains, through s2s.
RAM: more users, or users
RAM: more users, or users with bigger rosters consume more memory
CPU: users more active (send or receive more stanzas) consume more CPU
file descriptors: this is simple to solve, just configure your system to support more
network: if your users connect to many different remote servers, then obviously your machine must keep more connections open