Pub/sub limitations (no persistence) in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a key limitation of Redis Pub/Sub regarding message delivery?

Redis Pub/Sub does not store messages. If a subscriber is offline when a message is published, it will miss that message.

beginner

Why can't Redis Pub/Sub guarantee message delivery to all subscribers?

Because Redis Pub/Sub sends messages only to currently connected subscribers and does not save messages for later delivery.

intermediate

How does Redis Pub/Sub handle message persistence?

Redis Pub/Sub does not support message persistence; messages are transient and lost if no subscriber is listening at publish time.

intermediate

What happens if a subscriber disconnects and then reconnects in Redis Pub/Sub?

The subscriber will not receive any messages published while it was disconnected because Redis Pub/Sub does not store messages.

advanced

Name one alternative to Redis Pub/Sub if message persistence is required.

Redis Streams or message brokers like RabbitMQ or Kafka, which support message persistence and replay.

What happens to messages in Redis Pub/Sub if no subscriber is connected at publish time?

A Messages are stored and delivered later

B Messages are lost immediately

C Messages are queued until a subscriber connects

D Messages are saved to disk

Redis Pub/Sub does not store messages; if no subscriber is connected, messages are lost.

Which feature is NOT supported by Redis Pub/Sub?

A Real-time message delivery

B Message persistence

C Multiple subscribers

D Topic-based messaging

Redis Pub/Sub does not support message persistence; messages are transient.

If a subscriber disconnects, what happens to messages published during that time in Redis Pub/Sub?

A They are delivered when the subscriber reconnects

B They are stored in a queue

C They are lost

D They are sent to other subscribers only

Messages published while a subscriber is disconnected are lost because Redis Pub/Sub has no persistence.

Which Redis feature can be used if you need message persistence instead of Pub/Sub?

A Redis Lists

B Redis Streams

C Redis Sets

D Redis Hashes

Redis Streams support message persistence and replay, unlike Pub/Sub.

Why might Redis Pub/Sub be unsuitable for critical message delivery?

A It is too slow

B It requires complex setup

C It does not guarantee message delivery

D It only supports one subscriber

Redis Pub/Sub does not guarantee message delivery because it lacks persistence.

Explain the main limitation of Redis Pub/Sub related to message persistence and delivery.

Think about what happens if a subscriber is offline.

Describe alternatives to Redis Pub/Sub when message persistence is needed and why.

Consider systems designed for guaranteed delivery.