Messages within a partition are read in order. Partitions themselves may be read simultaneously or out of order. This is the trade-off for scalability. You can

Messages within a partition are read in order. Partitions themselves may be read simultaneously or out of order. This is the trade-off for scalability. You can compromise by using hashing or other logic to group related messages into the same partition. For example, hashing by user-id lets you process events for a particular user in order, while processing all events by users in parallel. If you can divide into logically consistent but globally isolated boundaries then this setup works very well.