Integration / Apache Pulsar Interview questions
How does Key_Shared subscription maintain ordering?
Key_Shared allows multiple consumers on one subscription, similar to Shared, but instead of pure round-robin distribution it hashes each message's key and consistently routes all messages sharing that key to the same consumer.
Ordering is preserved per key - all events for a given order ID or user ID, for example, always arrive at one consumer in the order they were published - while different keys can still be processed in parallel across multiple consumers.
If a consumer holding certain key ranges disconnects, Pulsar reassigns those key ranges to the remaining active consumers, preserving the per-key ordering guarantee even as the consumer set changes.
Key_Shared preserves ordering:
Messages are routed to a consistent consumer based on:
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