AP systems are the distributed storage systems tuned for availability. Designed as highly-responsive systems, they can sacrifice consistency, if needed, to accommodate high-velocity data. This means that these are distributed storage systems that are designed to immediately handle requests from users. Typical user requests are to read or write fast-changing data. Typical AP systems are used in real-time monitoring systems such as sensor networks. 

High-velocity distributed databases, such as Cassandra, are good examples of AP systems.

Let's look into where an AP system can be used. If Transport Canada wants to monitor traffic on one of the highways in Ottawa through a network of sensors installed at different locations on the highway, an AP system is recommended for implementing distributed data storage.