Subscriptions: Multiple Groups of Consumers on a Pulsar Topic

Apache Pulsar supports multiple groups of consumers (or consumer groups) on a topic, allowing multiple applications to consume messages from a single topic simultaneously. This is achieved through subscriptions that manage consumers on topics and keep track of their positions in the topic. A topic can support many subscriptions at once, each with one or more consumers. Pulsar offers four types of subscriptions: exclusive, failover, shared, and key_shared, which vary based on how messages are sent to consumers within a subscription. This feature enables message fan-out to multiple applications by simply adding subscriptions to the topic.