1. A system for monitoring a plurality of storage systems comprising: an interface, the interface specifying a common set of methods for performing storage commands on the plurality of storage systems; an implementation of the interface for each of the plurality of storage systems, the plurality of storage systems comprising at least two different types of storage systems, wherein a first implementation of the interface for a first one of the at least two different types of storage systems and a second implementation of the interface for a second one of the at least two different types of storage systems are configured to process a plurality of requests received from one or more applications that are directed to the at least two different types of storage systems by utilizing the common set of methods for performing storage commands on the at least two different types of storage systems; and a performance monitor configured: to monitor performance of requests for at least one of a plurality of classes of requests; to generate an alert characterizing performance of at least one of the plurality of classes of requests for at least one of the plurality of storage systems; and to provide the alert to at least one of the one or more applications to dynamically switch an application workload of said at least one application between two or more of the plurality of storage systems; wherein the interface is key-value based and the performance monitor is implemented as an extension of the key-value interface by using a same computer code to implement the performance monitor for monitoring the first and second storage systems; wherein the same computer code used to implement the performance monitor for monitoring the first and second storage systems comprises a constructor that takes as input a first parameter indicating a given one of the plurality of storage systems and a second parameter indicating a number of data points to keep for each of the plurality of classes of requests; and wherein the system is implemented using at least one processing device comprising a processor coupled to a memory.