Hi, I have a few questions regarding the order of processing when using processAsync.
>From the LinkedIn article here <https://engineering.linkedin.com/blog/2017/01/asynchronous-processing-and-multithreading-in-apache-samza--part> it mentions the following: "For parallelism within a task, Samza guarantees processAsync will be invoked in order for a task. The processing or completion, however, can go out of order. With this guarantee, users can implement sub-task-level data pipelining with customized ordering and parallelism. For example, users can use a keyed single thread executor pool to have in-order processing per key while processing messages with different keys in parallel." 1. What exactly is meant by a "keyed single thread executor pool"? Are there any code examples available on what this looks like? 2. I need to process a stream keyed on user IDs in parallel using processAsync but would like each user's event be processed in order. Does this then require custom ordering logic mentioned in the article? Thanks, Xiaochuan Yu
