All 7 Keyspace Notifications questions
More in Keyspace Notifications
How do you enable keyspace notifications in Redis, and what do the different configuration character options represent? How do you subscribe to and handle a specific type of keyspace notification, such as being alerted whenever a key expires? What are the reliability limitations of keyspace notifications that developers should understand before relying on them for critical application logic? What practical use cases in a real application are well suited to keyspace notifications despite their delivery limitations? How would you build a reliable cache invalidation system using keyspace notifications, while accounting for their delivery limitations? What performance considerations should you keep in mind when enabling keyspace notifications on a high throughput Redis instance?
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Redis › Keyspace Notifications

What are keyspace notifications in Redis, and what do they let your application do?

Beginner

Answer

Keyspace notifications let Redis publish events whenever certain operations happen to keys, such as a key being set, deleted, or expiring, letting other parts of your application subscribe to and react to these changes in real time, rather than needing to constantly poll Redis to check if something has changed.
CONFIG SET notify-keyspace-events 'KEA'
SUBSCRIBE __keyevent@0__:expired
Real-world example A shopping cart application listens for expired key events, automatically cleaning up related order data whenever a customer's abandoned cart session expires, without needing a separate polling process.

Common follow-ups: Why are keyspace notifications disabled by default in Redis?;What is the performance impact of enabling keyspace notifications on a busy server?

Pub/Sub;Expiration & Eviction
All 7 Keyspace Notifications questions