Using a bloom filters for api key verification

[vipoxin]

I know it sounds stupid and it really propably is, but, given that for every user that has his own key u:a:<userid>. The type could be a hashtable that is indexed in with the api key (the user id is known to user an posseses no security risk in disclosing), but that would mean i would literally have to store something just for the return value not not be nil and the auth to pass, for now i have nothing to cache as all operations eventually write to db and so there is no use in caching any of the permissions.
Would it be a bad idea to use a bloom filter that contains all the viable api keys for such user instead of hashtable?