Data Types: Structures That Solve Problems

Lists

LPUSH queue task-1        # push to head
RPUSH queue task-2        # push to tail
LRANGE queue 0 -1         # all items in order
LPOP queue                # pop from head

Lists make fifo queues and recent-activity feeds.

Sets

SADD online user-42
SISMEMBER online user-42   # 1
SINTER group1 group2       # common users
SCARD online               # count

Sets handle uniqueness, tags and membership checks.

Sorted Sets

ZADD scores 100 alice 200 bob
ZREVRANGE scores 0 2 WITHSCORES   # top 3
ZINCRBY scores 50 alice           # incremental update
ZSCORE scores alice

Sorted sets power leaderboards, queues with priority and rate limiting by score.

Hashes

HSET user:42 name "Alice" role "admin"
HGET user:42 name
HGETALL user:42
HINCRBY user:42 "visits" 1

Hashes store objects as fields, and partial updates touch no extra payload.

Key Points

• Lists queue; sets deduplicate; hashes model objects.
• Sorted sets rank by score atomically.
• Every type has atomic operations for counters.
• Pick the type that fits the read/write pattern.