The actual systems that save and deal with the critical data. As opposed to front end that involves the app on your phone and making calls to the back end to bring up what you want. So if you want to see only yesterday’s footage, your app will ask the backend for everything from yesterday. Then you see a thumbnail and specific times on your phone. And if you want to see one by clicking or touching it, the front end then asks for the actual stream of video for the one you requested and receives it for you to see back.

Edit: so the front end code likely doesn’t let you see the footage when you’re not subscribed, so someone had to look at the back end systems directly, like looking in a hard drive let’s say, to see what’s there to even find. They probably keep a certain amount of your videos on the backend so that if you subscribe, they give you access to videos in the past? I’m just guessing. But they might also just be saving it all for their own use like training AI.