Redis vs Memcached — which cache to use

Two Dominant Choices

Both are in-memory key-value stores. Choose Memcached for pure caching simplicity; choose Redis when you need more than caching.

Redis Advantages

• Rich data types: strings, hashes, lists, sets, sorted sets, streams
• Optional persistence (RDB snapshots, AOF write-ahead log)
• Pub/Sub for real-time messaging
• Atomic operations: INCR, SETNX, ZADD
• Lua scripting for complex atomic operations
• Redis Cluster for horizontal sharding

# Redis atomic counter (rate limiting)
INCR user:123:requests
EXPIRE user:123:requests 60

# Sorted set for leaderboard
ZADD leaderboard 1500 'user:alice'
ZADD leaderboard 2100 'user:bob'
ZREVRANGE leaderboard 0 9 WITHSCORES  # top 10

Memcached Advantages

• Multi-threaded: better CPU utilization on multi-core machines
• Simpler mental model: strings only
• Lower memory overhead per connection

When to Use Memcached

Pure read cache for simple string data at very high scale where multi-threaded performance matters. Most teams default to Redis due to its versatility. Memcached is rarely the right answer in 2024 unless you're already operating at massive scale.