Saurik has posted some comments regarding the way the Cydia jailbreak store functions and why some of the processes act the way they do, specifically the black loading bar you see upon first launching Cydia. He goes on to compare how Cydia loads data to how the App Store loads data and why they're different.
The biggest complaint we see from jailbreakers is how long Cydia takes to load their data. Jay Freeman has posted up some comments that explain a bit better how Cydia handles packages in comparison to the App Store.
While Apple chooses to only load 25 apps on any one page, Cydia actually loads the entire database of packages in real time. This is why you can scroll through so many packages at once and in one go as opposed to the App Store way of doing things which is by tapping a Load More.. button continuously to load 25 more applications.
"...Cydia, unlike the App Store (or almost any similar service), stores the entire package catalog locally. This is why it can (quite quickly, in fact) render an insanely long table with all packages in it that you can just fling your way through, while the App Store shows you 25 packages at a time with a slow "load more" button."
He goes further on to explain that a lot of how Cydia loads can heavily depend on what repositories you have added within Cydia. While Saurik has actively made suggestions as to how repos should be hosted, that doesn't mean all developers choose that route. If a source is offline or not available, that's when you'll get errors. I tested this theory by removing all repositories from my device except the big 3 - BigBoss, ModMyi, and ZodTTD. Cydia definitely loaded a lot quicker in comparison. It was almost instantaneous.
"Users are honestly more willing to believe they don't have the right source installed (as to them there are so many and they think they should have all of them on their phone... there are users out there with over 50 sources installed... I can't imagine what their refresh time must be like) than that they need to refresh some weird offline database."
In short, if you'd like your data to refresh a lot quicker, limit the amount of repositories you install to the ones you need. He also goes on to explain that new devices with faster processors obviously speed up the process as well. You can hit the link below to read the entire explanation of how Cydia data is handled.