A mechanism is disclosed for determining, based on a deterministic mechanism and a session's key value, a backup server for the session. In one embodiment, each session has a different key value, and each key value can be processed through the deterministic mechanism to give rise to a separate ordering of a result value set. Each server of a plurality of servers is associated with a different one of the set's values. A request pertaining to a particular session is received. The request indicates the particular session's key value. The deterministic mechanism can generate result values, in a particular order to which the session's key value gives rise, until a result value associated with a currently operational server is generated. The request is sent to that server if the request's primary server is not currently operational. A pseudo-random number generator seeded with the key value may generate the result values.