Keyv API

Table of Contents

Simple key-value storage with support for multiple backends

build codecov npm npm

Keyv provides a consistent interface for key-value storage across multiple backends via storage adapters. It supports TTL based expiry, making it suitable as a cache or a persistent key-value store.

Features

There are a few existing modules similar to Keyv, however Keyv is different because it:

  • Isn't bloated
  • Has a simple Promise based API
  • Suitable as a TTL based cache or persistent key-value store
  • Easily embeddable inside another module
  • Works with any storage that implements the Map API
  • Handles all JSON types plus Buffer
  • Supports namespaces
  • Wide range of efficient, well tested storage adapters
  • Connection errors are passed through (db failures won't kill your app)
  • Supports the current active LTS version of Node.js or higher

Table of Contents

Usage

Install Keyv.

npm install --save keyv

By default everything is stored in memory, you can optionally also install a storage adapter.

npm install --save @keyv/redis
    npm install --save @keyv/valkey
    npm install --save @keyv/mongo
    npm install --save @keyv/sqlite
    npm install --save @keyv/postgres
    npm install --save @keyv/mysql
    npm install --save @keyv/etcd
    npm install --save @keyv/memcache
    npm install --save @keyv/dynamo

First, create a new Keyv instance.

import Keyv from 'keyv';

Type-safe Usage

You can create a Keyv instance with a generic type to enforce type safety for the values stored. Additionally, both the get and set methods support specifying custom types for specific use cases.

Example with Instance-level Generic Type:

const keyv = new Keyv<number>(); // Instance handles only numbers
    await keyv.set('key1', 123);
    const value = await keyv.get('key1'); // value is inferred as number

Example with Method-level Generic Type:

You can also specify a type directly in the get or set methods, allowing flexibility for different types of values within the same instance.

const keyv = new Keyv(); // Generic type not specified at instance level
    
    await keyv.set<string>('key2', 'some string'); // Method-level type for this value
    const strValue = await keyv.get<string>('key2'); // Explicitly typed as string
    
    await keyv.set<number>('key3', 456); // Storing a number in the same instance
    const numValue = await keyv.get<number>('key3'); // Explicitly typed as number

This makes Keyv highly adaptable to different data types while maintaining type safety.

Using Storage Adapters

Once you have created your Keyv instance you can use it as a simple key-value store with in-memory by default. To use a storage adapter, create an instance of the adapter and pass it to the Keyv constructor. Here are some examples:

// redis
    import KeyvRedis from '@keyv/redis';
    
    const keyv = new Keyv(new KeyvRedis('redis://user:pass@localhost:6379'));

You can also pass in a storage adapter with other options such as ttl and namespace (example using sqlite):

//sqlite
    import KeyvSqlite from '@keyv/sqlite';
    
    const keyvSqlite = new KeyvSqlite('sqlite://path/to/database.sqlite');
    const keyv = new Keyv({ store: keyvSqlite, ttl: 5000, namespace: 'cache' });

To handle an event you can do the following:

// Handle DB connection errors
    keyv.on('error', err => console.log('Connection Error', err));

Now lets do an end-to-end example using Keyv and the Redis storage adapter:

import Keyv from 'keyv';
    import KeyvRedis from '@keyv/redis';
    
    const keyvRedis = new KeyvRedis('redis://user:pass@localhost:6379');
    const keyv = new Keyv({ store: keyvRedis });
    
    await keyv.set('foo', 'expires in 1 second', 1000); // true
    await keyv.set('foo', 'never expires'); // true
    await keyv.get('foo'); // 'never expires'
    await keyv.delete('foo'); // true
    await keyv.clear(); // undefined

It's is just that simple! Keyv is designed to be simple and easy to use.

Namespaces

You can namespace your Keyv instance to avoid key collisions and allow you to clear only a certain namespace while using the same database.

const users = new Keyv(new KeyvRedis('redis://user:pass@localhost:6379'), { namespace: 'users' });
    const cache = new Keyv(new KeyvRedis('redis://user:pass@localhost:6379'), { namespace: 'cache' });
    
    await users.set('foo', 'users'); // true
    await cache.set('foo', 'cache'); // true
    await users.get('foo'); // 'users'
    await cache.get('foo'); // 'cache'
    await users.clear(); // undefined
    await users.get('foo'); // undefined
    await cache.get('foo'); // 'cache'

Events

Keyv is a custom EventEmitter and will emit an 'error' event if there is an error. If there is no listener for the 'error' event, an uncaught exception will be thrown. To disable the 'error' event, pass emitErrors: false in the constructor options.

const keyv = new Keyv({ emitErrors: false });

In addition it will emit clear and disconnect events when the corresponding methods are called.

const keyv = new Keyv();
    const handleConnectionError = err => console.log('Connection Error', err);
    const handleClear = () => console.log('Cache Cleared');
    const handleDisconnect = () => console.log('Disconnected');
    
    keyv.on('error', handleConnectionError);
    keyv.on('clear', handleClear);
    keyv.on('disconnect', handleDisconnect);

Hooks

Keyv supports hooks for get, set, and delete methods. Hooks are useful for logging, debugging, and other custom functionality. Here is a list of all the hooks:

PRE_GET
    POST_GET
    PRE_GET_MANY
    POST_GET_MANY
    PRE_SET
    POST_SET
    PRE_DELETE
    POST_DELETE

You can access this by importing KeyvHooks from the main Keyv package.

import Keyv, { KeyvHooks } from 'keyv';
    
//PRE_SET hook
    const keyv = new Keyv();
    keyv.hooks.addHandler(KeyvHooks.PRE_SET, (data) => console.log(`Setting key ${data.key} to ${data.value}`));
    
    //POST_SET hook
    const keyv = new Keyv();
    keyv.hooks.addHandler(KeyvHooks.POST_SET, ({key, value}) => console.log(`Set key ${key} to ${value}`));

In these examples you can also manipulate the value before it is set. For example, you could add a prefix to all keys.

const keyv = new Keyv();
    keyv.hooks.addHandler(KeyvHooks.PRE_SET, (data) => {
      console.log(`Manipulating key ${data.key} and ${data.value}`);
      data.key = `prefix-${data.key}`;
      data.value = `prefix-${data.value}`;
    });

Now this key will have prefix- added to it before it is set.

In PRE_DELETE and POST_DELETE hooks, the value could be a single item or an Array. This is based on the fact that delete can accept a single key or an Array of keys.

Custom Serializers

Keyv uses buffer for data serialization to ensure consistency across different backends.

You can optionally provide your own serialization functions to support extra data types or to serialize to something other than JSON.

const keyv = new Keyv({ serialize: JSON.stringify, deserialize: JSON.parse });

Warning: Using custom serializers means you lose any guarantee of data consistency. You should do extensive testing with your serialisation functions and chosen storage engine.

If you do not want to use serialization you can set the serialize and deserialize functions to undefined. This will also turn off compression.

const keyv = new Keyv();
    keyv.serialize = undefined;
    keyv.deserialize = undefined;

Official Storage Adapters

The official storage adapters are covered by over 150 integration tests to guarantee consistent behaviour. They are lightweight, efficient wrappers over the DB clients making use of indexes and native TTLs where available.

Database Adapter Native TTL
Redis @keyv/redis Yes
Valkey @keyv/valkey Yes
MongoDB @keyv/mongo Yes
SQLite @keyv/sqlite No
PostgreSQL @keyv/postgres No
MySQL @keyv/mysql No
Etcd @keyv/etcd Yes
Memcache @keyv/memcache Yes
DynamoDB @keyv/dynamo Yes

Third-party Storage Adapters

You can also use third-party storage adapters or build your own. Keyv will wrap these storage adapters in TTL functionality and handle complex types internally.

import Keyv from 'keyv';
    import myAdapter from 'my-adapter';
    
    const keyv = new Keyv({ store: myAdapter });

Any store that follows the Map api will work.

new Keyv({ store: new Map() });

For example, quick-lru is a completely unrelated module that implements the Map API.

import Keyv from 'keyv';
    import QuickLRU from 'quick-lru';
    
    const lru = new QuickLRU({ maxSize: 1000 });
    const keyv = new Keyv({ store: lru });

The following are third-party storage adapters compatible with Keyv:

Using BigMap to Scale

Understanding JavaScript Map Limitations

JavaScript's built-in Map object has a practical limit of approximately 16.7 million entries (2^24). When you try to store more entries than this limit, you'll encounter performance degradation or runtime errors. This limitation is due to how JavaScript engines internally manage Map objects.

For applications that need to cache millions of entries in memory, this becomes a significant constraint. Common scenarios include:

  • High-traffic caching layers
  • Session stores for large-scale applications
  • In-memory data processing of large datasets
  • Real-time analytics with millions of data points

Why BigMap?

@keyv/bigmap solves this limitation by using a distributed hash approach with multiple internal Map instances. Instead of storing all entries in a single Map, BigMap distributes entries across multiple Maps using a hash function. This allows you to scale beyond the 16.7 million entry limit while maintaining the familiar Map API.

Key Benefits:

  • Scales beyond Map limits: Store 20+ million entries without issues
  • Map-compatible API: Drop-in replacement for standard Map
  • Performance: Uses efficient DJB2 hashing for fast key distribution
  • Type-safe: Built with TypeScript and supports generics
  • Customizable: Configure store size and hash functions

Using BigMap with Keyv

BigMap can be used directly with Keyv as a storage adapter, providing scalable in-memory storage with full TTL support.

Installation

npm install --save keyv @keyv/bigmap

Basic Usage

The simplest way to use BigMap with Keyv is through the createKeyv helper function:

import { createKeyv } from '@keyv/bigmap';
    
    const keyv = createKeyv();
    
    // Set values with TTL (time in milliseconds)
    await keyv.set('user:1', { name: 'Alice', email: '[email protected]' }, 60000); // Expires in 60 seconds
    
    // Get values
    const user = await keyv.get('user:1');
    console.log(user); // { name: 'Alice', email: '[email protected]' }
    
    // Delete values
    await keyv.delete('user:1');
    
    // Clear all values
    await keyv.clear();

For more details about BigMap, see the @keyv/bigmap documentation.

Compression

Keyv supports gzip, brotli and lz4 compression. To enable compression, pass the compress option to the constructor.

import Keyv from 'keyv';
    import KeyvGzip from '@keyv/compress-gzip';
    
    const keyvGzip = new KeyvGzip();
    const keyv = new Keyv({ compression: keyvGzip });
    
import Keyv from 'keyv';
    import KeyvBrotli from '@keyv/compress-brotli';
    
    const keyvBrotli = new KeyvBrotli();
    const keyv = new Keyv({ compression: keyvBrotli });
    
import Keyv from 'keyv';
    import KeyvLz4 from '@keyv/compress-lz4';
    
    const keyvLz4 = new KeyvLz4();
    const keyv = new Keyv({ compression: keyvLz4 });

You can also pass a custom compression function to the compression option. Following the pattern of the official compression adapters.

Want to build your own CompressionAdapter?

Great! Keyv is designed to be easily extended. You can build your own compression adapter by following the pattern of the official compression adapters based on this interface:

interface CompressionAdapter {
    	async compress(value: any, options?: any);
    	async decompress(value: any, options?: any);
    	async serialize(value: any);
    	async deserialize(value: any);
    }

In addition to the interface, you can test it with our compression test suite using @keyv/test-suite:

import { keyvCompresstionTests } from '@keyv/test-suite';
    import KeyvGzip from '@keyv/compress-gzip';
    
    keyvCompresstionTests(test, new KeyvGzip());

API

new Keyv([storage-adapter], [options]) or new Keyv([options])

Returns a new Keyv instance.

The Keyv instance is also an EventEmitter that will emit an 'error' event if the storage adapter connection fails.

storage-adapter

Type: KeyvStorageAdapter

Default: undefined

The connection string URI.

Merged into the options object as options.uri.

.namespace

Type: String Default: 'keyv'

This is the namespace for the current instance. When you set it it will set it also on the storage adapter. This is the preferred way to set the namespace over .opts.namespace.

options

Type: Object

The options object is also passed through to the storage adapter. Check your storage adapter docs for any extra options.

options.namespace

Type: String

Default: 'keyv'

Namespace for the current instance.

options.ttl

Type: Number

Default: undefined

Default TTL. Can be overridden by specififying a TTL on .set().

options.compression

Type: @keyv/compress-

Default: undefined

Compression package to use. See Compression for more details.

options.serialize

Type: Function

Default: JSON.stringify

A custom serialization function.

options.deserialize

Type: Function

Default: JSON.parse

A custom deserialization function.

options.store

Type: Storage adapter instance

Default: new Map()

The storage adapter instance to be used by Keyv.

Keyv Instance

Keys must always be strings. Values can be of any type.

.set(key, value, [ttl])

Set a value.

By default keys are persistent. You can set an expiry TTL in milliseconds.

Returns a promise which resolves to true.

.setMany(entries)

Set multiple values using KeyvEntrys { key: string, value: any, ttl?: number }.

.get(key, [options])

Returns a promise which resolves to the retrieved value.

.getMany(keys, [options])

Returns a promise which resolves to an array of retrieved values.

options.raw - (Will be deprecated in v6)

Type: Boolean

Default: false

If set to true the raw DB object Keyv stores internally will be returned instead of just the value.

This contains the TTL timestamp.

NOTE: This option will be deprecated in v6 and replaced with .getRaw() and .getManyRaw() methods.

.getRaw(key)

Returns a promise which resolves to the raw stored data for the key or undefined if the key does not exist or is expired.

.getManyRaw(keys)

Returns a promise which resolves to an array of raw stored data for the keys or undefined if the key does not exist or is expired.

.delete(key)

Deletes an entry.

Returns a promise which resolves to true if the key existed, false if not.

.deleteMany(keys)

Deletes multiple entries. Returns a promise which resolves to an array of booleans indicating if the key existed or not.

.clear()

Delete all entries in the current namespace.

Returns a promise which is resolved when the entries have been cleared.

.iterator()

Iterate over all entries of the current namespace.

Returns a iterable that can be iterated by for-of loops. For example:

// please note that the "await" keyword should be used here
    for await (const [key, value] of this.keyv.iterator()) {
      console.log(key, value);
    };

API - Properties

.namespace

Type: String

The namespace for the current instance. This will define the namespace for the current instance and the storage adapter. If you set the namespace to undefined it will no longer do key prefixing.

const keyv = new Keyv({ namespace: 'my-namespace' });
    console.log(keyv.namespace); // 'my-namespace'

here is an example of setting the namespace to undefined:

const keyv = new Keyv();
    console.log(keyv.namespace); // 'keyv' which is default
    keyv.namespace = undefined;
    console.log(keyv.namespace); // undefined

.ttl

Type: Number

Default: undefined

Default TTL. Can be overridden by specififying a TTL on .set(). If set to undefined it will never expire.

const keyv = new Keyv({ ttl: 5000 });
    console.log(keyv.ttl); // 5000
    keyv.ttl = undefined;
    console.log(keyv.ttl); // undefined (never expires)

.store

Type: Storage adapter instance

Default: new Map()

The storage adapter instance to be used by Keyv. This will wire up the iterator, events, and more when a set happens. If it is not a valid Map or Storage Adapter it will throw an error.

import KeyvSqlite from '@keyv/sqlite';
    const keyv = new Keyv();
    console.log(keyv.store instanceof Map); // true
    keyv.store = new KeyvSqlite('sqlite://path/to/database.sqlite');
    console.log(keyv.store instanceof KeyvSqlite); // true

.serialize

Type: Function

Default: JSON.stringify

A custom serialization function used for any value.

const keyv = new Keyv();
    console.log(keyv.serialize); // JSON.stringify
    keyv.serialize = value => value.toString();
    console.log(keyv.serialize); // value => value.toString()

.deserialize

Type: Function

Default: JSON.parse

A custom deserialization function used for any value.

const keyv = new Keyv();
    console.log(keyv.deserialize); // JSON.parse
    keyv.deserialize = value => parseInt(value);
    console.log(keyv.deserialize); // value => parseInt(value)

.compression

Type: CompressionAdapter

Default: undefined

this is the compression package to use. See Compression for more details. If it is undefined it will not compress (default).

import KeyvGzip from '@keyv/compress-gzip';
    
    const keyv = new Keyv();
    console.log(keyv.compression); // undefined
    keyv.compression = new KeyvGzip();
    console.log(keyv.compression); // KeyvGzip

.useKeyPrefix

Type: Boolean

Default: true

If set to true Keyv will prefix all keys with the namespace. This is useful if you want to avoid collisions with other data in your storage.

const keyv = new Keyv({ useKeyPrefix: false });
    console.log(keyv.useKeyPrefix); // false
    keyv.useKeyPrefix = true;
    console.log(keyv.useKeyPrefix); // true

With many of the storage adapters you will also need to set the namespace option to undefined to have it work correctly. This is because in v5 we started the transition to having the storage adapter handle the namespacing and Keyv will no longer handle it internally via KeyPrefixing. Here is an example of doing ith with KeyvSqlite:

import Keyv from 'keyv';
    import KeyvSqlite from '@keyv/sqlite';
    
    const store = new KeyvSqlite('sqlite://path/to/database.sqlite');
    const keyv = new Keyv({ store });
    keyv.useKeyPrefix = false; // disable key prefixing
    store.namespace = undefined; // disable namespacing in the storage adapter
    
    await keyv.set('foo', 'bar'); // true
    await keyv.get('foo'); // 'bar'
    await keyv.clear();

.throwOnErrors

Type: Boolean

Default: false

If set to true, Keyv will throw an error if any operation fails. This is useful if you want to ensure that all operations are successful and you want to handle errors.

const keyv = new Keyv({ throwOnErrors: true });
    console.log(keyv.throwOnErrors); // true
    keyv.throwOnErrors = false;
    console.log(keyv.throwOnErrors); // false

A good example of this is with the @keyv/redis storage adapter. If you want to handle connection errors, retries, and timeouts more gracefully, you can use the throwOnErrors option. This will throw an error if any operation fails, allowing you to catch it and handle it accordingly:

import Keyv from 'keyv';
    import KeyvRedis from '@keyv/redis';
    
    // create redis instance that will throw on connection error
    const keyvRedis = new KeyvRedis('redis://user:pass@localhost:6379', { throwOnConnectErrors: true });
    
    const keyv = new Keyv({ store: keyvRedis, throwOnErrors: true });

What this does is it only throw on connection errors with the Redis client.

.stats

Type: StatsManager

Default: StatsManager instance with enabled: false

The stats property provides access to statistics tracking for cache operations. When enabled via the stats option during initialization, it tracks hits, misses, sets, deletes, and errors.

Enabling Stats:

const keyv = new Keyv({ stats: true });
    console.log(keyv.stats.enabled); // true

Available Statistics:

  • hits: Number of successful cache retrievals
  • misses: Number of failed cache retrievals
  • sets: Number of set operations
  • deletes: Number of delete operations
  • errors: Number of errors encountered

Accessing Stats:

const keyv = new Keyv({ stats: true });
    
    await keyv.set('foo', 'bar');
    await keyv.get('foo'); // cache hit
    await keyv.get('nonexistent'); // cache miss
    await keyv.delete('foo');
    
    console.log(keyv.stats.hits);    // 1
    console.log(keyv.stats.misses);  // 1
    console.log(keyv.stats.sets);    // 1
    console.log(keyv.stats.deletes); // 1

Resetting Stats:

keyv.stats.reset();
    console.log(keyv.stats.hits); // 0

Manual Control:

You can also manually enable/disable stats tracking at runtime:

const keyv = new Keyv({ stats: false });
    keyv.stats.enabled = true; // Enable stats tracking
    // ... perform operations ...
    keyv.stats.enabled = false; // Disable stats tracking

How to Contribute

We welcome contributions to Keyv! 🎉 Here are some guides to get you started with contributing:

License

MIT © Jared Wray