Building A Distributed Timer Service At Scale: Handling 100k Timers...

The Timer Service is a distributed timer service capable of handling 100,000 timer creations per second with high precision and at-least-once delivery guarantees. Workers scan their partitions for soon-to-expire timers, load them into in-memory data structures for precise firing, then publish notifications to Kafka. ZooKeeper coordinates partition ownership among workers, preventing duplicate processing through ephemeral nodes.

Source: HackerNoon