Adaptive program task scheduling to blocking and non-blocking queues

Techniques are disclosed relating to scheduling program tasks in a server computer system. An example server computer system is configured to maintain first and second sets of task queues that have different performance characteristics, and to collect performance metrics relating to processing of program tasks from the first and second sets of task queues. Based on the collected performance metrics, the server computer system is further configured to update a scheduling algorithm for assigning program tasks to queues in the first and second sets of task queues. In response to receiving a particular program task associated with a user transaction, the server computer system is also configured to select the first set of task queues for the particular program task, and to assign the particular program task in a particular task queue in the first set of task queues.