A method and system for allocating and de-allocating memory for threads of an application is provided. An allocation system provides a heap for tracking free tokens of memory that are available for allocation to threads of an application. A heap tracks collections of free tokens of the fixed token size. The allocation system receives memory requests from threads that specify an allocation type of allocate or de-allocate. When multiple memory requests are pending concurrently from multiple threads, then the allocation system attempts to combine memory requests of the same type and of the same token size that are received from different threads. One of the threads is responsible for updating the heap to effect the two memory requests. The allocation system combines multiple memory requests so that the heap need only be accessed once to allocate or de-allocate multiple tokens.