When NetFlow is applied to an interface, which component creates the flow monitor cache that...

 A flow monitor is a component of Flexible NetFlow that is used to store and export flow data. A flow monitor consists of a record, an optional exporter, and a cache. The cache is a section of memory that stores flow entries before they are exported to an external collector. The cache is created by the flow monitor when NetFlow is applied to an interface. The cache collects traffic based on the key and nonkey fields in the configured record. The key fields are used to identify a flow uniquely, while the nonkey fields are used to provide additional information about the flow. The cache can be configured with various parameters, such as the number of entries, the timeout values, and the type of cache. The cache can also be viewed and cleared using show and clear commands. References :=

Some possible references are:

Flexible Netflow Configuration Guide, Cisco IOS Release 15M&T

ASR9000/XR Netflow Architecture and overview

Cisco IOS Flexible NetFlow Command Reference - cache (Flexible NetFlow) through match flow