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Vercel KV

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


npm install @vercel/kv


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 store
const client = getClient();
const store = new VercelKVStore({
// Define our encoder/decoder for converting between strings and Uint8Arrays
const 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(, index) => [
// Now you can get your messages from the store
const retrievedMessages = await store.mget(["message:id:0", "message:id:1"]);
// Make sure to decode the values
console.log( => 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:")) {
// The keys are not encoded, so no decoding is necessary
// Finally, let's delete the keys from the store
await store.mdelete(yieldedKeys);

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