# Is Cached?

## Contents
Overview Configuration

## Overview
The Is Cached? filter looks up a named cache to see if a specified message attribute has already been cached. A message attribute - usually message.key - is used as the key to search for in the cache. If the lookup succeeds, the retrieved value overrides a specified message attribute, which is usually the content.body attribute. For example, if a response message for a particular request has already been cached, the response message overrides the request message body so that it can be simply returned to the client using the Reflect filter. For more information on how to configure this filter in the context of a "caching circuit", please refer to the Global Caches tutorial.
## Configuration
Name: Enter a name for this filter here. Cache to Use: The list of currently configured caches will be displayed in the tree. Select the name of the cache to lookup to find the attribute specified in the Attribute containing key field below. Global caches (both local and distributed) can be added from the Caches top level node in the tree view of the Policy Studio. Attribute containing key: The message attribute entered here will be used as the key to lookup in the cache. In the context of a "caching circuit", the attribute entered here must be the same as the attribute specified in the Attribute key field on the Cache Attribute filter. Overwrite Attribute Name if Found: Usually the content.body is selected here so that value retrieved from the cache (which is usually a response message) overrides the request content.body with the cached response, which can then be returned to the client using the Reflect filter.