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Ankit malik
Ankit malik

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Redis cheatsheet

#redis #cheatsheet #database

Introduction

Redis is a powerful in-memory data structure store, commonly used as a database, cache, and message broker.

This is a quick reference guide containing the most commonly used Redis commands. If you are like me who often forget about commands when not using redis actively then it would be helpful.

Cheatsheet Commands

1. String

  • Use: Store simple values (text, numbers, JSON, etc.)
  • Commands: 
SET key value
GET key
INCR key     # increment number
DECR key     # decrement number
APPEND key value
DEL key
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2. List

  • Use: Ordered list of strings (like a queue or stack)
  • Commands: 
LPUSH key value   # add to head
RPUSH key value   # add to tail
LPOP key          # remove from head
RPOP key          # remove from tail
LRANGE key 0 -1   # get entire list
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3. Set

  • Use: Unordered collection of unique strings
  • Commands: 
SADD key value
SREM key value
SMEMBERS key
SISMEMBER key value
SUNION key1 key2
SINTER key1 key2
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4. Sorted Set (ZSet)

  • Use: Like a set, but each value has a score for sorting
  • Commands: 
ZADD key score member
ZRANGE key 0 -1        # get sorted elements
ZREM key member
ZSCORE key member
ZRANK key member
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5. Hash

  • Use: Store field–value pairs (like a mini JSON or dict)
  • Commands: 
HSET key field value
HGET key field
HGETALL key
HDEL key field
HMSET key field1 val1 field2 val2
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6. Fetch All keys 

KEYS *           # all keys
KEYS user:*      # keys that start with "user:"
KEYS *:profile   # keys that end with ":profile"
KEYS order:?     # keys like order:1, order:2 (one character wildcard)
KEYS session:[a-z]*  # regex-style pattern (for lowercase a-z)
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Scan is production safe

SCAN 0 MATCH user:* COUNT 100
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🔹 7. Hyperloglog Commands

Uses hyperloglog data structure under the hood. This helps in cardinality of any key and their members.
For example - You want to count the unique number likes for social media post.

# Add a like - 
PFADD <key> <element>
PFADD like:hll:post_123 user_456

# Get unique like count - 
PFCOUNT <key>
PFCOUNT like:hll:post_123

# Merge HLLs (e.g. across datacenters)
PFMERGE like:hll:post_123:global like:hll:post_123:dc1 like:hll:post_123:dc2
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