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MongoDB Chat Memory


Only available on Node.js.

You can still create API routes that use MongoDB with Next.js by setting the runtime variable to nodejs like so:

export const runtime = "nodejs";

You can read more about Edge runtimes in the Next.js documentation here.

For longer-term persistence across chat sessions, you can swap out the default in-memory chatHistory that backs chat memory classes like BufferMemory for a MongoDB instance.


You need to install Node MongoDB SDK in your project:

npm install -S mongodb
npm install @langchain/openai @langchain/community

You will also need a MongoDB instance to connect to.


Each chat history session stored in MongoDB must have a unique session id.

import { MongoClient, ObjectId } from "mongodb";
import { BufferMemory } from "langchain/memory";
import { ChatOpenAI } from "@langchain/openai";
import { ConversationChain } from "langchain/chains";
import { MongoDBChatMessageHistory } from "@langchain/mongodb";

const client = new MongoClient(process.env.MONGODB_ATLAS_URI || "", {
driverInfo: { name: "langchainjs" },
await client.connect();
const collection = client.db("langchain").collection("memory");

// generate a new sessionId string
const sessionId = new ObjectId().toString();

const memory = new BufferMemory({
chatHistory: new MongoDBChatMessageHistory({

const model = new ChatOpenAI({
model: "gpt-3.5-turbo",
temperature: 0,

const chain = new ConversationChain({ llm: model, memory });

const res1 = await chain.invoke({ input: "Hi! I'm Jim." });
console.log({ res1 });
res1: {
text: "Hello Jim! It's nice to meet you. My name is AI. How may I assist you today?"

const res2 = await chain.invoke({ input: "What did I just say my name was?" });
console.log({ res2 });

res1: {
text: "You said your name was Jim."

// See the chat history in the MongoDb
console.log(await memory.chatHistory.getMessages());

// clear chat history
await memory.chatHistory.clear();

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