If you have only two locations, you probably don't need to convert the full session ID into an integer, but just a small part or it. I recently had to build a kind of hashing function for splitting my processing of a very large data chunk into 10 sub-processes. One of the mandatory IDs of my data was a telephone number. I simply used the last digit of the phone number to decide to which process to allocate a given record and obtained an excellent load balancing. The advantage is that the simpler the splitting function is, the less performance overhead you get.