Read http://bretm.home.comcast.net/~bretm/hash/8.html (TL;DR: "CRC32 was never intended for hash table use. There is really no good reason to use it for this purpose, and I recommend that you avoid doing so").
Do you have that many unique queries that it warrants switching to something else besides MD5? If so, consider something more suitable besides CRC32, like MurmurHash or CityHash.