A system, method, and apparatus are provided for repartitioning a topic of a publish-subscribe message system. The topic is originally configured with N partitions (N>1) hosted by multiple brokers for storing messages to be consumed by multiple consumers. The repartitioning process causes one or more collections of partitions to be created in addition to the original collection of N partitions. Afterward, when a new message is received for the topic and has an associated partition key, the key is processed (e.g., hashed) once to identify a target collection of partitions and is then reprocessed to identify a destination partition within the target collection. Consumers may be automatically subscribed to new partitions. For example, a consumer subscribed to the ith partition of the original N partitions may be subscribed to the ith partition of each additional collection of partitions.
