I am building a customer database. The database will have a primary key. I am looking to make the primary key either a unique integer or a UUID (with 32 chars). The UUID appeals to me due to its ability to sync tables. The primary key will be used for (obviously): Searching and sorting records As a tag against documents eg document XX is linked to customer AA, BB and CC; and A foreign key to link tables My questions are: Do UUIDs adversely affect database size Do UUIDs adversely affect speed If UUIDs retain their full 32 chars, then there will obviously be a disadvantage. However, is FM clever enough to convert the UUID "under the hood" (such as to an integer referenced index) to improve database speed and/or size.