Essential Redis Commands

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Redis Commands(DOCUMENTATION)

Introduction

Redis commands are the building blocks of every interaction with the server. This lesson covers the essential commands for storing, retrieving, and managing keys ā€” the foundation you will use throughout every Redis project.

Key Concepts

  • SET/GET: Store and retrieve string values by key.
  • INCR/DECR: Atomically increment or decrement numeric values ā€” no race conditions.
  • EXPIRE/TTL: Set automatic key deletion after a timeout and check remaining time.
  • KEYS/EXISTS/DEL: Discover, check, and remove keys from the database.

Real World Context

These commands power the most common Redis patterns. SET/GET with EX handles session tokens, INCR drives page view counters and rate limiters, and EXPIRE ensures temporary data cleans itself up automatically.

Deep Dive

Let's learn the fundamental commands that form the foundation of working with Redis.

String Commands: SET and GET

Strings are the simplest Redis data type. Despite the name, they can store any data up to 512MB.

redis
# Basic SET and GET
SET user:name "Alice"
GET user:name
# Returns: "Alice"

# SET with options
SET session:abc123 "user_data" EX 3600  # Expires in 3600 seconds
SET lock:resource "locked" NX           # Only set if NOT exists
SET counter "100" XX                     # Only set if EXISTS

# Get multiple keys at once
MGET user:name session:abc123

Working with Numbers

Redis can treat strings as numbers for atomic operations:

redis
# Increment and decrement
SET views 0
INCR views           # Returns: 1
INCR views           # Returns: 2
INCRBY views 10      # Returns: 12
DECR views           # Returns: 11

# Float operations
SET price 19.99
INCRBYFLOAT price 0.50   # Returns: "20.49"

Key Management

redis
# Check if key exists
EXISTS user:name     # Returns: 1 (exists) or 0 (not exists)

# Delete keys
DEL user:name        # Returns: 1 (deleted) or 0 (didn't exist)
DEL key1 key2 key3   # Delete multiple keys

# Get key type
TYPE user:name       # Returns: string

# Rename a key
RENAME oldkey newkey

# Find keys by pattern (use carefully in production!)
KEYS user:*          # All keys starting with "user:"
KEYS *session*       # All keys containing "session"

Expiration (TTL)

Set automatic expiration on keys:

redis
# Set expiration when creating
SET session:token "abc" EX 3600      # 3600 seconds (1 hour)
SET temp:data "xyz" PX 30000         # 30000 milliseconds (30 seconds)

# Set expiration on existing key
EXPIRE user:session 1800             # 30 minutes
PEXPIRE user:session 1800000         # 30 minutes in milliseconds

# Set absolute expiration time
EXPIREAT key 1735689600              # Unix timestamp

# Check remaining time
TTL user:session     # Returns seconds remaining, -1 if no expiry, -2 if key doesn't exist
PTTL user:session    # Returns milliseconds remaining

# Remove expiration (make permanent)
PERSIST user:session

Useful String Operations

redis
# Get string length
STRLEN user:name     # Returns: 5 (for "Alice")

# Append to string
APPEND user:name " Smith"
GET user:name        # Returns: "Alice Smith"

# Get substring
GETRANGE user:name 0 4   # Returns: "Alice"

# Set multiple keys at once
MSET user:1:name "Bob" user:1:email "bob@example.com"

# Get multiple keys
MGET user:1:name user:1:email

Redis CLI Tips

bash
# Get help for any command
127.0.0.1:6379> HELP SET
127.0.0.1:6379> HELP @string    # All string commands

# Clear screen
127.0.0.1:6379> CLEAR

# See all command groups
127.0.0.1:6379> HELP @generic

šŸ“– Redis Commands Reference

Common Pitfalls

  1. Using KEYS in production ā€” KEYS * scans the entire keyspace and blocks Redis. Use SCAN for production key discovery.
  2. Forgetting that INCR creates keys ā€” INCR on a non-existent key creates it with value 0 then increments, which can lead to unexpected counters if your key naming has typos.

Best Practices

  1. Prefer SET with EX/NX options ā€” Combine value setting with expiration in a single atomic command instead of separate SET + EXPIRE calls.
  2. Use MGET/MSET for batch operations ā€” Reduce network round-trips by getting or setting multiple keys in one command.

Summary

  • SET and GET are the most fundamental Redis commands.
  • INCR provides atomic counters safe for concurrent access.
  • EXPIRE adds automatic TTL-based cleanup to any key.
  • TTL returns remaining seconds (-1 = no expiry, -2 = key missing).
  • Use SCAN instead of KEYS in production environments.

Code Examples

bash
SET user:name "Alice"
GET user:name
# "Alice"

SET session:token "abc" EX 3600
TTL session:token
# (integer) 3600

INCR page_views
# (integer) 1
āœ“ Completed