Key-Value Store

# Store a simple string
SET user:1000:name "Alice"

# Retrieve it
GET user:1000:name
# => "Alice"

# Store with expiration (10 seconds)
SET session:abc123 "user_data" EX 10

# Store only if key doesn't exist
SET counter:visitors 0 NX

# Increment a counter
INCR page_views
# => 1

INCRBY downloads 5
# => 5

# Decrement
DECR inventory:item42
# => 99

# Float increment
INCRBYFLOAT temperature 0.5
# => "23.5"

# Append to existing value
SET log "[INFO] "
APPEND log "Server started"
# => 20 (new length)

# Get string length
STRLEN log
# => 20

# Get substring
GETRANGE log 0 5
# => "[INFO]"

# Overwrite at offset
SETRANGE log 1 "WARN"

# Set multiple keys atomically
MSET user:1:name "Alice" user:2:name "Bob" user:3:name "Charlie"

# Get multiple keys
MGET user:1:name user:2:name user:3:name
# => ["Alice", "Bob", "Charlie"]

# Push to the head (left)
LPUSH queue:tasks "task1" "task2" "task3"
# => 3

# Push to the tail (right)
RPUSH queue:tasks "task4"
# => 4

# Pop from the head
LPOP queue:tasks
# => "task3"

# Pop from the tail
RPOP queue:tasks
# => "task4"

# Get list length
LLEN queue:tasks
# => 2

# Get range of elements (0-based, inclusive)
LRANGE queue:tasks 0 -1
# => ["task2", "task1"]

# Get element at index
LINDEX queue:tasks 0
# => "task2"

# Set element at index
LSET queue:tasks 0 "updated_task"

# Insert before/after pivot
LINSERT queue:tasks BEFORE "task1" "new_task"

# Remove elements
LREM queue:tasks 1 "task1"  # remove 1 occurrence

# Trim list to range
LTRIM queue:tasks 0 99  # keep first 100 items

# Set single field
HSET user:1000 name "Alice" age "30" city "NYC"
# => 3

# Get single field
HGET user:1000 name
# => "Alice"

# Get all fields and values
HGETALL user:1000
# => ["name", "Alice", "age", "30", "city", "NYC"]

# Get multiple fields
HMGET user:1000 name age
# => ["Alice", "30"]

# Get all field names
HKEYS user:1000
# => ["name", "age", "city"]

# Get all values
HVALS user:1000
# => ["Alice", "30", "NYC"]

# Check field existence
HEXISTS user:1000 email
# => 0

# Get field count
HLEN user:1000
# => 3

# Delete fields
HDEL user:1000 age
# => 1

# Increment numeric field
HINCRBY user:1000 login_count 1
# => 1

# Add members
SADD tags:post1 "rust" "database" "performance"
# => 3

# Check membership
SISMEMBER tags:post1 "rust"
# => 1

# Get all members
SMEMBERS tags:post1
# => ["rust", "database", "performance"]

# Union of sets
SADD tags:post2 "rust" "async" "tokio"
SUNION tags:post1 tags:post2
# => ["rust", "database", "performance", "async", "tokio"]

# Intersection
SINTER tags:post1 tags:post2
# => ["rust"]

# Difference
SDIFF tags:post1 tags:post2
# => ["database", "performance"]

# Get cardinality
SCARD tags:post1
# => 3

# Remove members
SREM tags:post1 "database"
# => 1

# Pop random member
SPOP tags:post1
# => "performance"

# Get random member without removing
SRANDMEMBER tags:post1
# => "rust"

# Set expiration in seconds
EXPIRE session:abc 3600

# Set expiration in milliseconds
PEXPIRE cache:user:1000 60000

# Get remaining TTL
TTL session:abc
# => 3599

# Remove expiration
PERSIST session:abc

# Check if key exists
EXISTS user:1000
# => 1

# Get value type
TYPE user:1000
# => hash

# Delete keys
DEL user:1000 user:1001
# => 2

# Rename key
RENAME old_key new_key

# Copy key
COPY source dest REPLACE

# Count keys in database
DBSIZE
# => 42

# Scan keys with pattern
SCAN 0 MATCH user:* COUNT 100

# List keys (use with caution in production)
KEYS user:*

# Flush database
FLUSHDB

/// Per-shard key-value store with full command execution.
///
/// `ShardStore` is the workhorse of the Kōra engine. Each shard worker thread
/// owns exactly one instance, so every operation runs single-threaded with no
/// locking. The store handles:
///
/// - String, list, hash, set, sorted set, stream, HyperLogLog, bitmap, and
///   geo commands.
/// - Lazy TTL expiration on access plus periodic bounded-sample sweeps.
/// - LFU-based eviction when a memory limit is configured.