8 Character Random Code

Question

I've been through answers to a few similar questions asked on SO, but could not find what I was looking for.

Is there a more efficient way to generate 8 character unique IDs, base 36 (0-9A-Z), than generating a unique ID and querying the DB to see if it already exists and repeating until you get a unique ID that has not been used?

Other solutions I found use time, but this is perhaps too easy to guess and may not work well in distributed systems. Consider these IDs to be promo codes.

Answer 1

One option is to do it the other way round: generate a huge number of them in the database whenever you need to, then either fetch a single one from the DB when you need one, or reserve a whole bunch of them for your particular process (i.e. mark them as "potentially used" in the database) and then dole them out from memory.