What is CQRS, and why would you consider using it?

CQRS (Command Query Responsibility Segregation) is a software pattern, which in its simplest form, looks at segregating Commands from Queries.

Most applications do far more reading from writing, and in this scenario, CQRS can really improve scalability. Databases do not normally scale easily or cheaply (in a cloud environment you may have to jump up a tier based on the resource usage, and this can quickly become costly!)