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What is redis-cli, and how do you use it to connect to and interact with a Redis server? What do the basic SET, GET, and DEL commands do in Redis? How do you check basic information about a Redis key, such as its data type and remaining time to live? How do you use the EXISTS and RENAME commands, and what should you be careful about when using RENAME? How would you use redis-cli's built-in monitoring and debugging features to troubleshoot a live performance issue on a production Redis instance? How do you use redis-cli in scripting mode to automate repetitive administrative tasks rather than running commands interactively?
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How do you search for keys matching a specific pattern in Redis, and why is the KEYS command generally discouraged in production?

Intermediate

Answer

You can use the KEYS command with a wildcard pattern to find matching key names, but it is generally discouraged in production because it scans the entire keyspace in a single blocking operation, which can significantly slow down the server on a large dataset, and the SCAN command is recommended instead since it iterates through the keyspace incrementally without blocking.
-- Avoid in production on a large dataset
KEYS user:*

-- Preferred alternative
SCAN 0 MATCH user:* COUNT 100
Real-world example A team investigating a brief production slowdown discovers a monitoring script had been calling KEYS on a large dataset, and switches it to use SCAN instead, eliminating the blocking behavior that was causing the issue.

Common follow-ups: How does SCAN's cursor based iteration actually work?;Are there any guarantees SCAN provides about not missing or duplicating keys?

Redis Memory Optimization;Redis Performance Tuning & Benchmarking
All 7 Redis CLI & Basic Commands questions