Scalable locality is when a system can use the same technology or method to make something work despite any changes in its size. For example, if you took a balloon and blew it up, the same technology, or 'method', of air pressure is being used, no matter how big the balloon got. This also works when it comes to computer systems. A system that is 'scalable' means it can work no matter how many people are using it or how much data is being stored. It can handle many different kinds of inputs - so it can be used by lots of people, or one person, and still give the same results.