What you want is a database that supports the equivalent of a multiple column key. You can fake it by concatenating your key with a time stamp. Tokyo cabinet

What you want is a database that supports the equivalent of a multiple column key. You can fake it by concatenating your key with a time stamp. Tokyo cabinet supports this with its btree+ store. You can select a range like thiskey-00000000 to thiskey-99999999. The latest is the last returned. Or give the latest the key thiskey-00000000 and rekey it when you do an update.