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What is a Redis Stream, and how does it differ from a regular Redis list when used as a messaging system? What is a consumer group in Redis Streams, and how does it enable multiple workers to process the same stream cooperatively? How do you acknowledge that a message read from a consumer group has been successfully processed? How do you limit the size of a Redis Stream to prevent it from growing indefinitely and consuming unlimited memory? How would you handle a message that was delivered to a consumer but never acknowledged, perhaps because that consumer crashed while processing it? How would you design a robust event sourcing system using Redis Streams as the primary event log?
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Redis › Streams

How do you add a new entry to a Redis Stream, and how do you read entries back from it?

Beginner

Answer

You use XADD to add a new entry, providing a set of field value pairs representing the message data, and XRANGE to read a range of entries from the stream, specifying starting and ending id boundaries, letting you retrieve all or a specific portion of the stream's stored history.
XADD orders '*' orderId '1001' status 'created'
XRANGE orders - +
Real-world example An order processing system adds a new stream entry every time an order's status changes, and a monitoring dashboard reads the full history of status changes for a specific order using XRANGE.

Common follow-ups: What is the format of the id automatically generated for each stream entry?;How do you read only the newest entries added since your last read?

Redis as a Message Queue;Data Types
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