Throttling, which limits the number of requests to a service to a manageable level, can be used to protect resource limited services such as compute intensive tasks or backend services with underlying resource restrictions, such as those making use of an FTP server for example. When many requests flood into an FTP server, the server will inherently slow down as the underlying storage system needs to perform expensive disk searches.
There are many examples of systems overloading due to high demand, none more so than those observed on Black Friday in 2016. Throttling is used to prevent systems from going down especially at peak times, which can be very costly for the reputation of a business.
Further details on the Black Friday melt ...
