No reason you can't do an inventory check at the same time as returning the basic catalogue details, it won't be more accurate in a separate call 50ms later. If

No reason you can't do an inventory check at the same time as returning the basic catalogue details, it won't be more accurate in a separate call 50ms later. If you're generating the page for a logged in user then you know who that logged in user is and what they're asking for, so you can calculate coupons and the like in the same call too without needing to resend the same parameters to the database to look up, and if not feed in a different parameter for their IP address. Now, I'm sure there's all sorts of other things in apps beyond my experience where you're better off doing multiple calls to the database, but certainly nothing you've outlined in those two couldn't be handled by a decent database infrastructure in a single call returning (potentially) multiple results sets. One thing I learnt many years ago in data intensive apps. Communications latency between your app and your database will kill performance if you let it. Shipping data back and forth repeatedly will hang, draw and quarter it. Absolutely, aggressively, pare the number of external calls you have to make to the bone and you'll see a very significant performance boost.