Not the same machines, but different groups or machines (pools, shards, farms, whatever). They'll certainly be able to move you around to balance the pools, or to decomission pools, or to put you in a pool with primary data closer to where you usually access from etc. Grouping by behavior makes sense too --- separating heavy and light users makes a lot of sense, you can serve a lot more light users from one pool, and the heavy users won't impact their service.