In accordance with an embodiment, described herein is a system and method for providing an asynchronous architecture in a server with an existing synchronous architecture. The system can include a keep-alive subsystem and a user-level request context switching application programming interface (API). A plurality of connections can be received at the keep-alive subsystem, and each connection can be assigned a request context configured to be executed in the keep-alive subsystem. When a connection being executed by a thread is blocked for I/O, the request context assigned to the connection can be saved, and the request context assigned to another connection can be restored to be executed by the thread. Resources associated with an idle connection can be placed in a pool for reuse by other connections. The system can provide an asynchronous architecture in the server without changing existing code and functionalities of the existing synchronous architecture.