Hi @N_C, if you want to use CDJs with djay, currently your only option is to connect them to a Mac. Unfortunately, CDJs are not currently USB Class Compliant so they are not compatible with iOS devices. For more details on how to set this up on Mac, please refer to the linked FAQ below:
https://help.algoriddim.com/hc/en-us/articles/360022122239-How-do-I-connect-djay-Pro-for-Mac-to-CDJs
Alternatively, if you want to use an iOS device, you might want to consider going the Laidback Luke route, and bringing a small form factor controller like the Reloop Mixtour Pro. This doesn’t take up much room in the booth, is easy to pack/transport and can simply be connected to the club mixer via RCA cables. There’s an in depth discussion of the Mixtour Pro below, plus Laidback Luke has a bunch of YouTube videos using this setup in clubs and at festivals. Personally, I prefer to bring my own gear to gigs because I know it works and I don’t have to depend on something that’s not within my control. I hope that helps!