What's a Counter Cache?

Nowadays users of modern web and mobile applications expect a fast response for each interaction. As developers, we need to be aware of the performance of our applications and how we can improve it. This involves constantly searching for potential bottlenecks, and especially looking for inefficient queries when we are dealing with large amounts of data.One of the most common performance issues in Rails applications is the N 1 query problem. This problem occurs when we are loading a collection of records and for each record we are running a separate query to count how many records are associated with that record.