The Event Sourcing Pattern is a technique used in software architecture that enables the ability to save changes to an application's state as a sequence of events. The Pattern is built on top of the Command Query Responsibility Segregation (CQRS) principle, which dictates that application functions for writing data (commands) should be separate from those for reading data (queries). Event Sourcing further expands upon CQRS by taking these ‘write’ operations one step further and storing them as a log or record list of all events following each other in succession. This provides an immutable record of any prior state and facilitates recreating instance lags or replaying sequences of past events. Essentially, the Event Sourcing Pattern allows developers to take advantage of even more granular control over how their applications are modified and operated. Thus, it has become an invaluable difference-maker when creating architecture solutions that need to run at maximum efficiency without sacrificing accuracy or reliability.