Redis

Add a database to store and retrieve data.

The Redis plugin is designed to be fast, scalable and secure, and it supports a subset of the full Redis API, including:

• Transactions for things like counting votes atomically in polls
• String operations for batch writing or incrementing numbers
• Sorted sets for creating leaderboards
• Hashes for managing a collection of key-value pairs

Each app version installed on a subreddit is namespaced, which means Redis data is siloed from other subreddits. Keep in mind that there won’t be a single source of truth for all installations of your app, since each app installation can only access the data that it has stored in the Redis database.

note

Redis is a more robust replacement for the key value store. All apps using the key value store should migrate to Redis.

Limits and Quotas

• Max commands per second: 1000
• Max request size: 5 MB
• Max storage: 500 MB

All limits are applied at a per-installation granularity.

Add Redis to your app

When creating an app, enable the plugin in Devvit.configure.

Devvit.configure({
  redis: true,
});

note

For existing apps, learn how to migrate the KV store to Redis.

Examples

Menu items

Devvit.addMenuItem({
  location: 'subreddit',
  label: 'Test Redis',
  onPress: async (event, { redis }) => {
    const key = 'hello';
    await redis.set(key, 'world');
    const value = await redis.get(key);
    console.log(`${key}: ${value}`);
  },
});

Custom Posts

You can follow this template to create a custom post containing an interactive progress bar backed by Redis.

// start from a template
devvit new <replace-with-your-app-name> --template=redis
devvit playtest <your-test-subreddit>

Supported Redis commands

note

Not all Redis features are supported. If you would like to request a specific Redis feature, please reach out to our team via modmail or Discord.

Simple read/write

Command	Action
get	Gets the value of key.
set	Sets key to hold a string value.
del	Removes the specified keys.
type	Returns the string representation of the type of value stored at key.

Batch read/write

Command	Action
mget	Returns the values of all specified keys.
mset	Sets the given keys to their respective values.

Strings

Command	Action
getRange	Returns the substring of the string value stored at key, determined by the offsets start and end (both are inclusive).
setRange	Overwrites part of the string stored at key, starting at the specified offset, for the entire length of value.
strlen	Returns the length of the string value stored at key.

Hash

Redis hashes can store upto ~ 4.2 billion key-value pairs. We recommend hash usage for managing collections of key/value pairs whenever possible and iterating over it using a combination of hscan, hkeys and hgetall - this will also allow you easily migrate away from using kvStore.list method. Please see the migration guide for more details.

Command	Action
hget	Returns the value associated with field in the hash stored at key.
hset	Sets the specified fields to their respective values in the hash stored at key.
hdel	Removes the specified fields from the hash stored at key.
hgetall	Returns a map of fields and their values stored in the hash
hkeys	Returns all field names in the hash stored at key.
hscan	Iterates fields of Hash types and their associated values.
hincrby	Increments the score of member in the sorted set stored at key by value
hlen	Returns the number of fields contained in the hash stored at key.

Numbers

Command	Action
incrBy	Increments the number stored at key by increment.

Key expiration

Command	Action
expire	Sets a timeout on key.
expireTime	Returns the absolute Unix timestamp (since January 1, 1970) in seconds at which the given key will expire.

Transactions

Redis transactions allow execution of a group of commands in a single isolated step. For example, let’s say you are implementing voting action in a polls app. These three steps need to happen together:

• Store the selected option for the user
• Increment the count for selected option
• Add the user to voted user list

We can sequence all of the above steps in a single transaction using multi and exec to ensure that either all of the steps happen together or none at all.

Command	Action
multi	Marks the start of a transaction block.
exec	Executes all previously queued commands in a transaction and restores the connection state to normal.
discard	Flushes all previously queued commands in a transaction and restores the connection state to normal.
watch	Marks the given keys to be watched for conditional execution of a transaction.
unwatch	Flushes all the previously watched keys for a transaction.

Sorted set

Command	Action
zAdd	Adds all the specified members with the specified scores to the sorted set stored at key.
zCard	Returns the sorted set cardinality (number of elements) of the sorted set stored at key.
zRange	Returns the specified range of elements in the sorted set stored at key.
zRem	Removes the specified members from the sorted set stored at key.
zScore	Returns the score of member in the sorted set at key.
zRank	Returns the rank of member in the sorted set stored at key
zIncrBy	Increments the score of member in the sorted set stored at key by value
zScan	Iterates elements of sorted set types and their associated scores.
zRemByRangeByLex	When all elements in a sorted set are inserted with the same score, this command removes the elements at key between the lexicographical range specified by min and max.
zRemByRangeByRank	Removes all elements in the sorted set stored at key with rank between start and stop.
zRemByRangeByScore	Removes all elements in the sorted set stored at key with a score between min and max (inclusive).