Most commercial Web sites dynamically generate their contents through a three-tier server architecture composed of a Web server, an application server, and a database server. In such an architecture, the database server may become a bottleneck to the overall performance. In this dissertation, we propose WDBAccel, an accelerator that significantly improves the throughput of database processing. WDBAccel eliminates costly, complex query processing needed to obtain query results by reusing the results from previous queries for subsequent queries. This differentiates WDBAccel from other database cache systems, which employ traditional query processing. WDBAccel further improves its performance by fully utilizing main memory as the primary storage. We also propose an update management mechanism to ensure query results cached in WDBAccel consistent to the origin data in databases. We evaluate the performance of WDBAccel and compare it to other cache systems, Oracle and TimesTen, by using the TPC-W benchmark. The measurement results show that WDBAccel outperforms those cache systems by up to 16 times.