Roughly described, a database query router is installed transparently in a network between database client systems and a database server cluster. One subset of the servers is designated to handle read queries only and a second subset is designated to handle write queries. The query router receives, through a network port, the database queries made by a client system, and directed to the IP address and port assigned to the query router. The query router determines whether the query is a read or a write query, and forwards read queries to servers in the first subset and write queries to servers in the second subset of servers. By installing the query router transparently in the network, no modifications are required to the software in either the client systems or the database servers in order to add query routing functionality to a client/server database environment.