Importance

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Abstract

A method and system are provided for caching data in a manner that substantially maintains a desired level of system performance. A cache server receives data requests on behalf of a data server. When new data on the data server is generated or stored that replaces or changes data cached on the cache server, the corresponding data on the cache server is invalidated. A subsequent request for the new data may be forwarded to the data server or may be served with the invalid data on the cache server. Determining how to serve the request may depend on a possible impact on system performance and/or one or more characteristics or parameters associated with the requested data. The impact on system performance may be determined by examining actual and/or desired operating conditions (e.g., rate or number of requests, load on the data server, response time to requests, number of open connections, throughput). The data parameters that may be considered may include the popularity of the data; frequency of access to the data; number of accesses; age, size, or type of the data; whether or when a version of the data on the cache server is invalid; how severely invalid the cache server version is; the cost of retrieving the data from the data server; etc. One request received for the new data may be forwarded to the data server in order to receive the new data, cache it and return in to the requester. In order to promote performance, however, any number of requests for new data that is to replace cached data (even a first request received after the cached data is invalidated) may be served with cache data that is responsive but invalid.

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First Claim