✨ "How to Enable a Replica Set in MongoDB on Coolify (for Prisma ORM Compatibility)" (#1160)

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Co-authored-by: svenja.michal <84835304+svenja11@users.noreply.github.com>

Author: technotip

tutorials/prisma-mongodb-replica-set/01.en.md

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+---
+SPDX-License-Identifier: MIT
+path: "/tutorials/prisma-mongodb-replica-set"
+slug: "prisma-mongodb-replica-set"
+date: "2025-06-13"
+title: "How to Enable a Replica Set in MongoDB on Coolify (for Prisma ORM Compatibility)"
+short_description: "Learn how to enable a MongoDB replica set on Coolify to make it compatible with Prisma ORM, even for single-node deployments."
+tags: ["MongoDB", "Prisma"]
+author: "Satish"
+author_link: "https://github.com/technotip"
+author_img: "https://avatars.githubusercontent.com/u/4805549"
+author_description: ""
+language: "en"
+available_languages: ["en"]
+header_img: "header-6"
+cta: "cloud"
+---
+
+## Introduction
+
+If you're using **Prisma ORM** with **MongoDB**, you may encounter an unexpected blocker: Prisma **requires MongoDB to be part of a replica set** — even if you're only running a single-node deployment. This requirement is non-negotiable, and without a replica set, Prisma simply won't work with MongoDB.
+
+In this article, we’ll walk you through how to **enable a single-node replica set** on a MongoDB instance hosted via **Coolify** on your VPS. This is the simplest workaround for Prisma’s replica set dependency when you're not running a full production-ready MongoDB cluster.
+
+**Why Prisma Requires a Replica Set**
+
+Prisma uses features like transactions and change streams, which require MongoDB to be deployed as a replica set — even if you’re using just one node. This doesn’t mean you have to set up multiple MongoDB instances; you can configure a **replica set on a single-node** MongoDB server to satisfy Prisma’s requirements.
+
+**Prerequisites**
+
+* Coolify is already installed (see [this tutorial](https://community.hetzner.com/tutorials/install-and-configure-coolify-on-linux))
+* You've deployed a [MongoDB](https://coolify.io/docs/databases/#deploy-a-database) database
+* Your app uses [Prisma](https://www.prisma.io/)
+
+## Step 1 - Access Your Coolify Dashboard
+
+Log into your Coolify instance.
+
+You should have a project with a MongoDB resource and a server where Coolify is running on.
+
+![](images/coolify-dashboard.png)
+
+## Step 2 - Generate a Secure Keyfile
+
+The replica set requires a shared keyfile for internal authentication, even if it's just one node.
+
+1. In the dashboard, select the server **where Coolify itself is running**.
+2. Switch to the terminal tab.
+3. Run the following command to generate a 741-byte base64 key:
+
+   ```bash
+   openssl rand -base64 741
+   ```
+
+4. Create a new file:
+
+   ```bash
+   nano keyfile-mongo
+   ```
+
+5. Paste the generated key and save the file.
+6. Secure the keyfile with proper permissions:
+
+   ```bash
+   chmod 400 keyfile-mongo
+   chown 999:999 keyfile-mongo
+   ```
+
+7. Create a directory to store the keyfile and move it there:
+
+   ```bash
+   mkdir -p /root/replica
+   mv keyfile-mongo /root/replica/replica.key
+   ```
+
+## Step 3 - Mount the Keyfile in Your MongoDB Instance
+
+1. In the Coolify dashboard, select the project with MongoDB and open your MongoDB instance.
+2. Go to **Persistent Storage**.
+3. Click **+ Add** to add a new volume:
+
+   - **Name**: `replica`
+   - **Source Path**: `/root/replica`
+   - **Destination Path**: `/tmp/mongodb`
+
+This mounts your keyfile inside the MongoDB container.
+
+![](images/mount-keyfile.png)
+
+## Step 4 - Update the MongoDB Configuration
+
+1. Go to the **General** tab for your MongoDB instance.
+2. Scroll down to **Custom MongoDB Configuration**, and enter:
+
+   ```yaml
+   replication:
+     replSetName: "rs0"
+   security:
+     authorization: enabled
+     keyFile: /tmp/mongodb/replica.key
+   ```
+   
+   ![](images/mongodb-config.png)
+
+## Step 5 - Enable Replica Set Initialization
+
+1. Start your MongoDB instance.
+1. Go to the **Terminal** tab for your MongoDB instance.
+3. Connect to the MongoDB server:
+   ```bash
+   mongosh -u root -p <mongodb_password> --authenticationDatabase admin
+   ```
+4. Now run:
+   
+   > Replace `27017` with the port of your MongoDB instance.
+   
+   ```js
+   rs.initiate({
+     _id: "rs0",
+     members: [{ _id: 0, host: "localhost:27017" }],
+   });
+   ```
+
+3. Save and restart your MongoDB service.
+
+## Step 6 - Testing the Setup
+
+After restarting MongoDB:
+
+1. Connect to the MongoDB server:
+   ```bash
+   mongosh -u root -p <mongodb_password> --authenticationDatabase admin
+   ```
+
+2. Run:
+   ```js
+   rs.status();
+   ```
+
+3. Confirm that the replica set is active.
+4. Test your Prisma application to ensure the connection works.
+
+## Step 7 - Production Considerations (Optional)
+
+This tutorial sets up a **single-node replica set** to satisfy Prisma’s requirements. For high availability and production-grade environments, consider setting up a **three-node replica set** across separate containers or servers.
+
+## Conclusion
+
+You've now configured MongoDB with a **single-node replica set** in Coolify, ensuring full compatibility with Prisma ORM — without the complexity of managing multiple MongoDB instances. This setup is ideal for local development, staging, or lightweight production use cases.
+
+When you're ready to scale, transitioning to a true multi-node replica set will be straightforward.
+
+##### License: MIT
+
+<!--
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+(a) The contribution was created in whole or in part by me and I have
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+Signed-off-by: [Satish <satish@technotip.org>]
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