In the previous chapter, we wired up a reactive cart and modeled a complete local signal-based data flow. That was a useful foundation, but real applications rarely operate in isolation. At some point, the cart needs to talk to the outside world, loading product details from a server, persisting items, or syncing across devices. These operations are inherently asynchronous, and this is where signals really start to show their strength. Now, we are moving into async territory.