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Generic commands operate on keys regardless of their data type. These commands handle key lifecycle, expiration, pattern matching, and type inspection.

​
DEL

Deletes one or more keys.

​
Syntax

DEL key [key ...]
​
key
key
required
The key(s) to delete. Multiple keys can be specified.
​
integer
integer
The number of keys that were removed.
Time Complexity: O(N) where N is the number of keys. For string keys, O(1) per key. For other types, O(M) where M is the number of elements.

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Examples

redis> SET key1 "Hello"
OK
redis> SET key2 "World"
OK
redis> DEL key1 key2 key3
(integer) 2

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EXISTS

Determines whether one or more keys exist.

​
Syntax

EXISTS key [key ...]
​
key
key
required
The key(s) to check. Multiple keys can be specified.
​
count
integer
Number of keys that exist. If the same key is mentioned multiple times, it will be counted multiple times.
Time Complexity: O(N) where N is the number of keys to check. History:
  • 3.0.3: Accepts multiple key arguments.

​
Examples

redis> SET key1 "Hello"
OK
redis> EXISTS key1
(integer) 1
redis> EXISTS nosuchkey
(integer) 0
redis> SET key2 "World"
OK
redis> EXISTS key1 key2 nosuchkey
(integer) 2

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EXPIRE

Sets the expiration time of a key in seconds.

​
Syntax

EXPIRE key seconds [NX | XX | GT | LT]
​
key
key
required
The key to set expiration on.
​
seconds
integer
required
The expiration time in seconds.
​
NX
option
Set expiry only when the key has no expiry.
​
XX
option
Set expiry only when the key has an existing expiry.
​
GT
option
Set expiry only when the new expiry is greater than current one.
​
LT
option
Set expiry only when the new expiry is less than current one.
​
result
integer
  • 1 if the timeout was set
  • 0 if the timeout was not set (key doesn’t exist or condition not met)
Time Complexity: O(1) History:
  • 7.0.0: Added options: NX, XX, GT and LT.

​
Examples

redis> SET mykey "Hello"
OK
redis> EXPIRE mykey 10
(integer) 1
redis> TTL mykey
(integer) 10
redis> SET mykey "Hello World"
OK
redis> TTL mykey
(integer) -1
redis> EXPIRE mykey 10 XX
(integer) 0
redis> TTL mykey
(integer) -1
redis> EXPIRE mykey 10 NX
(integer) 1
redis> TTL mykey
(integer) 10

​
TTL

Returns the remaining time to live of a key in seconds.

​
Syntax

TTL key
​
key
key
required
The key to get TTL for.
​
ttl
integer
  • TTL in seconds
  • -1 if the key exists but has no associated expire
  • -2 if the key does not exist
Time Complexity: O(1) History:
  • 2.8.0: Added the -2 reply.

​
Examples

redis> SET mykey "Hello"
OK
redis> EXPIRE mykey 10
(integer) 1
redis> TTL mykey
(integer) 10
redis> SET mykey "Hello" EX 30
OK
redis> TTL mykey
(integer) 30

​
KEYS

Returns all key names that match a pattern.

​
Syntax

KEYS pattern
​
pattern
pattern
required
The glob-style pattern to match. Supported patterns:
  • * matches any characters
  • ? matches a single character
  • [abc] matches one character from the set
  • [a-z] matches one character from the range
  • \ escapes special characters
​
keys
array
List of keys matching the pattern.
Time Complexity: O(N) where N is the number of keys in the database.
KEYS should not be used in production code as it blocks the server. Use SCAN instead for iterating keys.

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Examples

redis> MSET firstname Jack lastname Stuntman age 35
OK
redis> KEYS *name*
1) "firstname"
2) "lastname"
redis> KEYS a??
1) "age"
redis> KEYS *
1) "firstname"
2) "age"
3) "lastname"

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SCAN

Iterates over the key names in the database using a cursor.

​
Syntax

SCAN cursor [MATCH pattern] [COUNT count] [TYPE type]
​
cursor
integer
required
The cursor position. Use 0 to start iteration.
​
MATCH
option
Only return keys matching the given pattern.
​
COUNT
option
Hint for how many elements to return per call (default 10).
​
TYPE
option
Only return keys of this type (string, list, set, zset, hash, stream).
​
result
array
Array with two elements:
  1. The next cursor position (0 when iteration is complete)
  2. Array of keys
Time Complexity: O(1) for each call. O(N) for complete iteration where N is the number of keys. History:
  • 6.0.0: Added the TYPE subcommand.

​
Examples

redis> SCAN 0
1) "17"
2)  1) "key:12"
    2) "key:8"
    3) "key:4"
    4) "key:14"
    5) "key:16"
    6) "key:17"
    7) "key:15"
    8) "key:10"
    9) "key:3"
   10) "key:7"
   11) "key:1"
redis> SCAN 17
1) "0"
2) 1) "key:5"
   2) "key:18"
   3) "key:0"
   4) "key:2"
   5) "key:19"
   6) "key:13"
   7) "key:6"
   8) "key:9"
   9) "key:11"
redis> SCAN 0 MATCH key:1* COUNT 100
1) "0"
2) 1) "key:12"
   2) "key:18"
   3) "key:11"
   4) "key:15"
   5) "key:17"
   6) "key:1"
   7) "key:16"
   8) "key:14"
   9) "key:19"
  10) "key:10"
  11) "key:13"
redis> SCAN 0 TYPE string
1) "0"
2) 1) "key:0"
   2) "key:2"
   3) "key:1"

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TYPE

Determines the type of value stored at a key.

​
Syntax

TYPE key
​
key
key
required
The key to inspect.
​
type
string
Type of the key:
  • string
  • list
  • set
  • zset (sorted set)
  • hash
  • stream
  • none (key doesn’t exist)
Time Complexity: O(1)

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Examples

redis> SET key1 "value"
OK
redis> LPUSH key2 "value"
(integer) 1
redis> SADD key3 "value"
(integer) 1
redis> TYPE key1
string
redis> TYPE key2
list
redis> TYPE key3
set
redis> TYPE nosuchkey
none
  • PERSIST: Remove expiration from a key
  • EXPIREAT: Set expiration as Unix timestamp
  • PEXPIRE: Set expiration in milliseconds
  • PTTL: Get TTL in milliseconds
  • RENAME: Rename a key
  • RENAMENX: Rename a key only if new key doesn’t exist
  • DUMP: Serialize key value
  • RESTORE: Deserialize key value
  • TOUCH: Update last access time
  • UNLINK: Async delete

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Best Practices

​
Key Naming

  1. Use consistent naming conventions (e.g., object:id:field)
  2. Keep names readable but concise
  3. Use colons to separate logical parts
  4. Avoid special characters

​
Expiration

  1. Always set TTL on temporary data
  2. Use EXPIRE with conditions (NX, XX, GT, LT) for precise control
  3. Monitor expired keys with INFO stats

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Iteration

  1. Always use SCAN instead of KEYS in production
  2. Use MATCH patterns to filter results
  3. Adjust COUNT for optimal performance
  4. Handle full iterations by checking cursor = 0
DEL is synchronous and can block the server for large keys. Consider using UNLINK for async deletion of large keys.

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