Connection examples

The examples below connect and run a simple operation with the official MongoDB drivers for Node.js, Python, and Go.

None of them hardcodes a URI. Each one reads MONGODB_URI from the environment, so the same code works with the connection string the Operator generated for you - whatever the cluster name, namespace, replica set name, or TLS setting happens to be. Take the URI from Connect your application and put it in the environment first:

export MONGODB_URI=$(kubectl get secret <connection-secret-name> -n <namespace> \
  -o jsonpath='{.data.<username>_mongos_connectionString}' | base64 --decode)

On a replica set cluster the key is <username>_rs0_connectionString instead. See Connection secrets for the full key layout.

Node.js

Use the MongoDB Node.js driver. Install it with:

npm install mongodb

Example: connect and insert one document.

const { MongoClient } = require("mongodb");

const uri = process.env.MONGODB_URI;

async function run() {
  const client = new MongoClient(uri);
  try {
    await client.connect();
    const db = client.db("mydb");
    const result = await db.collection("items").insertOne({ name: "example", value: 1 });
    console.log("Inserted id:", result.insertedId);
  } finally {
    await client.close();
  }
}

run().catch(console.error);

The Operator’s replica set connection string already carries replicaSet=rs0, so the driver handles failover and reconnection without any extra code.

Python

Use PyMongo. Install it with:

pip install pymongo

Example: connect and insert one document.

import os
from pymongo import MongoClient

uri = os.environ["MONGODB_URI"]

client = MongoClient(uri)
try:
    db = client.mydb
    result = db.items.insert_one({"name": "example", "value": 1})
    print("Inserted id:", result.inserted_id)
finally:
    client.close()

Use the same URI format as in Connect your application. For replica set, include replicaSet=rs0 in the URI; PyMongo will discover members and handle failover.

Go

Use the MongoDB Go driver. Add the module:

go get go.mongodb.org/mongo-driver/mongo

Example: connect and insert one document.

package main

import (
    "context"
    "fmt"
    "log"
    "os"

    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

func main() {
    uri := os.Getenv("MONGODB_URI")

    client, err := mongo.Connect(context.Background(), options.Client().ApplyURI(uri))
    if err != nil {
        log.Fatal(err)
    }
    defer func() { _ = client.Disconnect(context.Background()) }()

    coll := client.Database("mydb").Collection("items")
    result, err := coll.InsertOne(context.Background(), bson.M{"name": "example", "value": 1})
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println("Inserted id:", result.InsertedID)
}

Use the same URI for replica set (with replicaSet=rs0); the driver handles replica set discovery and reconnection.

Keep the URI in an environment variable for the connection string

Do not hardcode the MongoDB URI or credentials in your code. Use environment variables (for example MONGODB_URI or MONGODB_USER and MONGODB_PASSWORD) so you can change them per environment (local, staging, production) without changing code.

Example:

export MONGODB_URI=$(kubectl get secret <connection-secret-name> -n <namespace> \
  -o jsonpath='{.data.<username>_mongos_connectionString}' | base64 --decode)

Taking the value from the Secret rather than typing a URI keeps the host, the replica set name, and the TLS settings correct without you tracking them. Your app reads the variable at startup. In Kubernetes, you can inject it from a Secret or ConfigMap.

Use a dedicated application user rather than the database admin account, with only the roles it needs. That limits the damage if the credentials leak.

Retries and connection pooling

MongoDB drivers support automatic retries and connection pooling. For replica sets, the driver can reconnect and fail over if the primary changes. See your driver’s documentation (for example Node.js, Python, Go) for options like connection timeouts and retry logic.

Next steps

Troubleshoot connection issues

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Last update: September 3, 2026
Created: February 13, 2026