Title : Optimizing Query Execution in Large-Scale Web Search 
Engines

Large web search engines have to answer thousands of queries 
per second with interactive response times. Due to the size 
of the data sets involved, usually in the range of multiple 
terabytes, a single query may require the processing of 
hundreds of megabytes of index data. To keep up with this 
immense workload, large search engines employ clusters of 
hundreds or thousands of machines, and techniques such as 
caching, index compression, and index and query pruning are 
used to improve scalability.

*Joint work with Xiaohui Long