A system may include a buffer monitor configured to monitor buffer content of a buffer being used during processing of a query workflow in which write tasks of the query workflow write data to the buffer and read tasks of the query workflow read data from the buffer, the buffer having a buffer capacity. The system may include a threshold manager configured to compare the buffer content to a low threshold and to a high threshold that are defined relative to the buffer capacity, and a speed controller configured to control a number of the write tasks relative to a number of the read tasks that are currently executing the query workflow, to thereby maintain the buffer content between the low threshold and the high threshold.