Web search engines have to deal with a rapidly increasing amount of information, high query loads and tight performance constraints.  ...  Third, we elaborate on caching in Web search engines in two independent contributions. First, we present an analytical model that finds the optimal split in a static memory-based two-level cache.  ...  Rocha-Junior for the useful advices and comments on the paper. Acknowledgments. This work was done while the second author was an intern at Yahoo!  ...