As far as I remember you needed quite big servers if you wanted to "federate" with others, like join big chatroom because Matrix will try to replicate the history and keep it in sync. Is it still the case?
Yes, if you want to participate in rooms with >10K users or >500 servers you need quite a large box (several GB of RAM) - although over the last few weeks we had several massive algorithmic performance breakthroughs which should help this a lot. these are currently being tested and implemented in Synapse (the python impl).
