keyv

What is keyv?

The keyv npm package is a simple key-value storage with support for multiple backends. It is designed to be a straightforward solution for key-value storage across different systems and protocols. It supports TTL based expiry, making it suitable for applications like caching and session storage.

What are keyv's main functionalities?

Simple Key-Value Storage

Store and retrieve data using simple key-value pairs.

{"const Keyv = require('keyv');
const keyv = new Keyv();
keyv.set('foo', 'bar').then(() => keyv.get('foo').then(value => console.log(value)));
// Logs: 'bar'"}

Namespaces

Use namespaces to avoid key collisions when sharing the same storage backend.

{"const Keyv = require('keyv');
const users = new Keyv('sqlite://path/to/database.sqlite', { namespace: 'users' });
const cache = new Keyv('sqlite://path/to/database.sqlite', { namespace: 'cache' });
// `users` and `cache` can share the same storage without key collisions."}

Support for Multiple Backends

Keyv can be used with various storage backends like Redis, MongoDB, SQLite, and more.

{"const Keyv = require('keyv');
const keyv = new Keyv('redis://user:pass@localhost:6379');
keyv.set('foo', 'bar').then(() => keyv.get('foo').then(value => console.log(value)));
// This will use Redis as the storage backend."}

TTL (Time to Live)

Automatically expire keys after a certain period of time.

{"const Keyv = require('keyv');
const keyv = new Keyv({ ttl: 10000 });
keyv.set('foo', 'expires in 10 seconds', 10000).then(() => setTimeout(() => keyv.get('foo').then(value => console.log(value)), 15000));
// Logs: undefined, since the key has expired after 10 seconds."}

Other packages similar to keyv

node-cache

node-cache is an in-memory key-value store similar to keyv but does not support multiple backends. It is purely for in-memory storage with TTL support.

levelup

levelup is a wrapper for LevelDB. It provides a key-value store with a rich set of features. Unlike keyv, levelup is more complex and is designed specifically for LevelDB.

ioredis

ioredis is a robust, performance-focused Redis client for Node.js. While keyv supports Redis as one of its backends, ioredis is dedicated solely to Redis and offers more advanced features specific to Redis.

memcached

memcached is a Node.js client for the memcached server. It is similar to keyv in providing a key-value cache but is specific to the memcached protocol and server.

README

Simple key-value storage with support for multiple backends

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

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/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

First, create a new Keyv instance.

import Keyv from 'keyv';

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. In addition it will emit a clear and disconnect event 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.addListener(KeyvHooks.PRE_SET, (key, value) => console.log(`Setting key ${key} to ${value}`));

//POST_SET hook
const keyv = new Keyv();
keyv.hooks.addListener(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.addListener(KeyvHooks.PRE_SET, (key, value) => {
  console.log(`Setting key ${key} to ${value}`);
  key = `prefix-${key}`;
});

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.

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
MongoDB	@keyv/mongo	Yes
SQLite	@keyv/sqlite	No
PostgreSQL	@keyv/postgres	No
MySQL	@keyv/mysql	No
Etcd	@keyv/etcd	Yes
Memcache	@keyv/memcache	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:

• quick-lru - Simple "Least Recently Used" (LRU) cache
• keyv-file - File system storage adapter for Keyv
• keyv-dynamodb - DynamoDB storage adapter for Keyv
• keyv-lru - LRU storage adapter for Keyv
• keyv-null - Null storage adapter for Keyv
• keyv-firestore – Firebase Cloud Firestore adapter for Keyv
• keyv-mssql - Microsoft Sql Server adapter for Keyv
• keyv-azuretable - Azure Table Storage/API adapter for Keyv
• keyv-arango - ArangoDB storage adapter for Keyv
• keyv-momento - Momento storage adapter for Keyv

Add Cache Support to your Module

Keyv is designed to be easily embedded into other modules to add cache support. The recommended pattern is to expose a cache option in your modules options which is passed through to Keyv. Caching will work in memory by default and users have the option to also install a Keyv storage adapter and pass in a connection string, or any other storage that implements the Map API.

You should also set a namespace for your module so you can safely call .clear() without clearing unrelated app data.

Inside your module:

class AwesomeModule {
	constructor(opts) {
		this.cache = new Keyv({
			uri: typeof opts.cache === 'string' && opts.cache,
			store: typeof opts.cache !== 'string' && opts.cache,
			namespace: 'awesome-module'
		});
	}
}

Now it can be consumed like this:

import AwesomeModule from 'awesome-module';

// Caches stuff in memory by default
const awesomeModule = new AwesomeModule();

// After npm install --save keyv-redis
const awesomeModule = new AwesomeModule({ cache: 'redis://localhost' });

// Some third-party module that implements the Map API
const awesomeModule = new AwesomeModule({ cache: some3rdPartyStore });

Compression

Keyv supports gzip and brotli 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 });

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?

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.

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-<compression_package_name>
Default: undefined

Compression package to use. See Compression for more details.

options.serialize

Type: Function
Default: JSONB.stringify

A custom serialization function.

options.deserialize

Type: Function
Default: JSONB.parse

A custom deserialization function.

options.store

Type: Storage adapter instance
Default: new Map()

The storage adapter instance to be used by 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.

.get(key, [options])

Returns a promise which resolves to the retrieved value.

options.raw

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.

.delete(key)

Deletes an entry.

Returns a promise which resolves to true if the key existed, false if 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);
};

How to Contribute

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

• Contributing - Learn about how to contribute to Keyv
• Code of Conduct - Learn about the Keyv Code of Conduct
• How to Contribute - How do develop in the Keyv mono repo!

License

MIT © Jared Wray