[Performance] how many user/traffic can mybb handle

[Dark-Power-Invader]

I am sure MyBB can handle the users but the fact your storage will be consumed before you ever reached that scale, i believe it won't be a problem for MyBB to handle request as for the MySQL part and cluster thing i guess it is possible by load balancing your MyBB can host on a different server and MySQL on a different one(better if MySQL is run over a SSD instead of HDD for faster performance). And for the competition i can only think of discourse who is quite fast and can handle same userbase as defined by OP on a single server but it also include the problem for storage run out.