Abstract: A database query system is provided. The database cache system includes: a network library which processes an access request issued by the online game server by using an input output completion port (IOCP); at least one database connection module which provides a connector for reading data from the database or recording data to the database; a database cache which stores data read from the database by the database connection module; and at least one cache buffer which is allotted to an IOCP worker thread corresponding to a database query request issued by the online game server and stores data read from the database, which is to be transmitted to the online game server.

Abstract: A VENUS (Virtual Environment Network User Simulator) system, including: a VC (Virtual Client) agent for managing a plurality of VCs and providing a monitoring result; a server observer for transmitting a state of a server system by a request or periodically; a client observer for transmitting a state of a client system by a request or periodically; a testing game client for transmitting a state of an application program by using an API (Application Program Interface) provided from an observer library; a testing game server cluster for transmitting a state of an application program using the API provided from the observer library; and a CES (Central Engineering Station) for receiving an input from a user to setup a simulation environment, managing the VC agent, monitoring a network state and the state of the server system through the server observer, and monitoring the state of the client system through the client observer.