A computer comprising one or more processors and memory implements a thread manager for multiple threads of an application. The thread manager may implement a process-local cache of standby threads for the application. Upon request to create a thread for the application, the thread manager may use a standby thread from the process-local cache to create the requested thread, initializing thread-local storage elements and scheduling the thread for execution. Upon request to terminate a thread of the application, the thread manager may place the thread in an unscheduled state and add the thread to the process-local cache of standby threads. The thread manager may also add or remove standby threads to the process-local cache of standby threads in the event the thread manager determines that the number of standby threads in the process-local cache lies outside a target range.