In the previous chapter, we began to develop a mental model of a Cassandra table that looked like a key-value store where each value is a collection of columns with values. Now that we have seen compound primary keys, we can refine that mental model to take into account the more complex structures we now know how to build, as follows:
We can envision the user_status_updates table as a more robust key-value structure. Our keys are still usernames, but the values are now ordered collections of rows, both identified and ordered by the id clustering column. As with our earlier model, each partition key's data stands alone; to get data from multiple partitions, we have to go looking in multiple places.