The Command and Query Responsibility Segregation (CQRS) pattern is an architectural pattern used for separating read operations from write operations within an application or system. The goal of this separation is to improve scalability by allowing both sets of operations to scale independently of each other. Furthermore, CQRS also improves flexibility by allowing for different approaches in implementing each set of operations as well as reliability by reducing latency in query responses due to the separate data stores being used for each type of operation. The core idea behind CQRS is that when a user interacts with an application or system, they will either be issuing a command or making a query. Commands are typically issued to modify data while queries are issued to retrieve data. By separating these two types of operations into two different models, each model can be optimized independently for its own specific purpose. This can lead to improved performance since querying and writing can take place in two separate databases which can be tuned and scaled independently from one another. By separating commands from queries, applications are able to better utilize resources such as memory and processing power since they won’t have to run both types of operations simultaneously on the same hardware or platform.  Additionally, using separate models for commands and queries allows developers more flexibility when it comes time to make changes as they can update one model without affecting the other. Finally, using CQRS makes applications more reliable since queries will not have any impact on commands which means that query responses will not be affected by any delays caused by writing data.