In addition to having multiple brokers working together, individual message streams are often split so the clients are load balanced across different parts of a stream of messages. This split of message streams is generally referred to as "partitioning".

Clients often send different messages targeted to the same stream to multiple partitions of the stream. The partition is often chosen either directly by the client, or the client may use a round-robin, or a hash of some value, to select a partition. Spreading the load across multiple partitions, allows the brokers to share the client load. The consumption of messages is an important design in a messaging system, and the choice from which partitions each consumer reads, must take into account how the partition is chosen for the producer of messages.