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*   Vercel KV

On this page

Vercel KV
=========

This example demonstrates how to setup chat history storage using the `VercelKVStore` `BaseStore` integration.

Setup[​](#setup "Direct link to Setup")
---------------------------------------

*   npm
*   Yarn
*   pnpm

    npm install @vercel/kv

    yarn add @vercel/kv

    pnpm add @vercel/kv

Usage[​](#usage "Direct link to Usage")
---------------------------------------

    import { createClient } from "@vercel/kv";import { VercelKVStore } from "@langchain/community/storage/vercel_kv";import { AIMessage, HumanMessage } from "@langchain/core/messages";// Pro tip: define a helper function for getting your client// along with handling the case where your environment variables// are not set.const getClient = () => {  if (!process.env.VERCEL_KV_API_URL || !process.env.VERCEL_KV_API_TOKEN) {    throw new Error(      "VERCEL_KV_API_URL and VERCEL_KV_API_TOKEN must be set in the environment"    );  }  const client = createClient({    url: process.env.VERCEL_KV_API_URL,    token: process.env.VERCEL_KV_API_TOKEN,  });  return client;};// Define the client and storeconst client = getClient();const store = new VercelKVStore({  client,});// Define our encoder/decoder for converting between strings and Uint8Arraysconst encoder = new TextEncoder();const decoder = new TextDecoder();/** * Here you would define your LLM and chat chain, call * the LLM and eventually get a list of messages. * For this example, we'll assume we already have a list. */const messages = Array.from({ length: 5 }).map((_, index) => {  if (index % 2 === 0) {    return new AIMessage("ai stuff...");  }  return new HumanMessage("human stuff...");});// Set your messages in the store// The key will be prefixed with `message:id:` and end// with the index.await store.mset(  messages.map((message, index) => [    `message:id:${index}`,    encoder.encode(JSON.stringify(message)),  ]));// Now you can get your messages from the storeconst retrievedMessages = await store.mget(["message:id:0", "message:id:1"]);// Make sure to decode the valuesconsole.log(retrievedMessages.map((v) => decoder.decode(v)));/**[  '{"id":["langchain","AIMessage"],"kwargs":{"content":"ai stuff..."}}',  '{"id":["langchain","HumanMessage"],"kwargs":{"content":"human stuff..."}}'] */// Or, if you want to get back all the keys you can call// the `yieldKeys` method.// Optionally, you can pass a key prefix to only get back// keys which match that prefix.const yieldedKeys = [];for await (const key of store.yieldKeys("message:id:")) {  yieldedKeys.push(key);}// The keys are not encoded, so no decoding is necessaryconsole.log(yieldedKeys);/**[  'message:id:2',  'message:id:1',  'message:id:3',  'message:id:0',  'message:id:4'] */// Finally, let's delete the keys from the storeawait store.mdelete(yieldedKeys);

#### API Reference:

*   [VercelKVStore](https://v02.api.js.langchain.com/classes/langchain_community_storage_vercel_kv.VercelKVStore.html) from `@langchain/community/storage/vercel_kv`
*   [AIMessage](https://v02.api.js.langchain.com/classes/langchain_core_messages.AIMessage.html) from `@langchain/core/messages`
*   [HumanMessage](https://v02.api.js.langchain.com/classes/langchain_core_messages.HumanMessage.html) from `@langchain/core/messages`

* * *

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