The OrderTransitionWorker acts as a locking mechanism to ensure an order can only be updated sequentially to avoid race conditions when receiving the accepted response from a request and asynchronously receiving the result of that request.

Below is an example of the sequence that can occur when creating an order:

send HTTP request to create order ->

                                <- asynchronously receive on stream that order created successfully
                                 <- response from HTTP request that create order was accepted

Multiple orders can be updated in parallel by using 2 or more workers. Orders are deterministically sent to the same worker using the following algorithm.

hash(order.client_id) % order_transition_worker_count