Memory with MongoDB

This example demonstrates how to use Mastra's memory system with MongoDB as the storage backend.

Prerequisites

This example uses the openai model and requires a MongoDB database. Make sure to add the following to your .env file:

OPENAI_API_KEY=<your-api-key>
MONGODB_URI=<your-connection-string>
MONGODB_DB_NAME=<your-db-name>

And install the following package:

npm install @mastra/mongodb

Adding memory to an agent

To add MongoDB memory to an agent use the Memory class and create a new storage key using MongoDBStore. The configuration supports both local and remote MongoDB instances.

import { Memory } from "@mastra/memory";
import { Agent } from "@mastra/core/agent";
import { openai } from "@ai-sdk/openai";
import { MongoDBStore } from "@mastra/mongodb";

export const mongodbAgent = new Agent({
  name: "mongodb-agent",
  instructions:
    "You are an AI agent with the ability to automatically recall memories from previous interactions.",
  model: openai("gpt-4o"),
  memory: new Memory({
    storage: new MongoDBStore({
      url: process.env.MONGODB_URI!,
      dbName: process.env.MONGODB_DB_NAME!,
    }),
    options: {
      threads: {
        generateTitle: true,
      },
    },
  }),
});

Vector embeddings with MongoDB

Embeddings are numeric vectors used by memory's semanticRecall to retrieve related messages by meaning (not keywords).

Note: You must use a deployment hosted on MongoDB Atlas to successfully use the MongoDB Vector database.

This setup uses FastEmbed, a local embedding model, to generate vector embeddings. To use this, install @mastra/fastembed:

npm install @mastra/fastembed

Add the following to your agent:

import { Memory } from "@mastra/memory";
import { Agent } from "@mastra/core/agent";
import { openai } from "@ai-sdk/openai";
import { MongoDBStore, MongoDBVector } from "@mastra/mongodb";
import { fastembed } from "@mastra/fastembed";

export const mongodbAgent = new Agent({
  name: "mongodb-agent",
  instructions:
    "You are an AI agent with the ability to automatically recall memories from previous interactions.",
  model: openai("gpt-4o"),
  memory: new Memory({
    storage: new MongoDBStore({
      url: process.env.MONGODB_URI!,
      dbName: process.env.MONGODB_DB_NAME!,
    }),
    vector: new MongoDBVector({
      uri: process.env.MONGODB_URI!,
      dbName: process.env.MONGODB_DB_NAME!,
    }),
    embedder: fastembed,
    options: {
      lastMessages: 10,
      semanticRecall: {
        topK: 3,
        messageRange: 2,
      },
      threads: {
        generateTitle: true, // generates descriptive thread titles automatically
      },
    },
  }),
});

Usage example

Use memoryOptions to scope recall for this request. Set lastMessages: 5 to limit recency-based recall, and use semanticRecall to fetch the topK: 3 most relevant messages, including messageRange: 2 neighboring messages for context around each match.

import "dotenv/config";

import { mastra } from "./mastra";

const threadId = "123";
const resourceId = "user-456";

const agent = mastra.getAgent("mongodbAgent");

const message = await agent.stream("My name is Mastra", {
  memory: {
    thread: threadId,
    resource: resourceId,
  },
});

await message.textStream.pipeTo(new WritableStream());

const stream = await agent.stream("What's my name?", {
  memory: {
    thread: threadId,
    resource: resourceId,
  },
  memoryOptions: {
    lastMessages: 5,
    semanticRecall: {
      topK: 3,
      messageRange: 2,
    },
  },
});

for await (const chunk of stream.textStream) {
  process.stdout.write(chunk);
}