Glitch File System Decision Guide: When to Use Local Storage vs External Databases

The Glitch File System Dilemma

When you build an app on Glitch, the first thing you notice is that the file system behaves differently from a typical local development environment. Glitch runs your code inside a container that has an ephemeral file system. Files you create through the web editor stay on disk after a restart, but any file you write programmatically during runtime can disappear when the project sleeps or the container is recreated.

Key Constraints

• Project Sleep: After a period of inactivity (usually about 5 minutes), Glitch puts the container into a dormant state to save resources. A request to the app wakes the container, which adds a short delay.
• Disk Quota: Each project is allocated a limited amount of disk space. Writing large amounts of data locally can exhaust this quota and cause the project to become unstable.
• Public Exposure: All files in a public project are readable by anyone, so secrets must never be stored in regular files.
• Latency Impact: The first request after a sleep period requires the container to start, which can add 1‑3 seconds of latency.

Storage Options Comparison

Feature	Local File System	External Database (MongoDB/Firebase)
Data Persistence	Not guaranteed – lost on sleep/restart	Guaranteed – survives all project states
Setup Complexity	Zero – files.write() works immediately	Moderate – requires connection configuration
Performance	Fastest I/O for small files	Network‑dependent, slight latency
Security	Public by default – secrets at risk	Controlled access via credentials
Scalability	Limited by disk quota	Highly scalable
Use Cases	Caching, temporary files, logs	User data, application state, configs

Decision Framework

Use the local file system when:

• You need temporary caching or session storage that can be rebuilt.
• Writing log files for debugging, knowing they may disappear.
• Generating static assets that can be recreated on each start.
• Handling small, non‑critical files that stay well within the quota.

Integrate external storage when:

• You need guaranteed data persistence beyond a single container lifecycle.
• Storing user‑generated content or application state that must survive sleeps.
• Handling sensitive information like API keys or credentials.
• Planning for production deployment or scaling the application.

Concrete Implementation: External Database Setup

Below is a step‑by‑step example that shows how to add MongoDB as a persistent store in a Glitch project.

1. Install Dependencies – Open the project terminal (or edit package.json) and run:

npm install mongodb dotenv

This adds the MongoDB driver and the dotenv package for loading environment variables.

2. Configure Environment Variables – Create a .env file in the project root with the connection string placeholder:

MONGODB_URI=your_mongodb_connection_string_here

Replace your_mongodb_connection_string_here with the URI you obtain from your MongoDB Atlas cluster or other provider. The .env file is automatically loaded by dotenv and is not committed to the public repository.

3. Implement Database Connection – Add a new file db.js:

const { MongoClient } = require('mongodb');
require('dotenv').config();

const client = new MongoClient(process.env.MONGODB_URI);

async function connect() {
  await client.connect();
  return client.db('myApp').collection('data');
}

module.exports = { connect, client };

This code creates a client, connects to the database, and exports a function to obtain the target collection.

4. Use in Your Application – Example Express route that saves data:

const express = require('express');
const { connect } = require('./db');
const app = express();

app.use(express.json());

app.post('/save', async (req, res) => {
  const collection = await connect();
  await collection.insertOne({ data: req.body.data });
  res.send('Data saved');
});

app.listen(3000, () => console.log('Server running on port 3000'));

Validation Strategy

To confirm that your storage choice works as expected, follow these verification steps:

1. Test Persistence – Write a file using fs.writeFile, then restart the project from the settings panel or wait for it to sleep. Check the file tree to see if the file still exists.
2. Monitor Logs – Deploy a simple Express server (as shown above) and watch the console logs when the project wakes after a sleep period. Look for the “Server running” message and any connection attempts.
3. Check Environment Variables – Open the project settings panel and verify that the .env file is listed and that the MONGODB_URI variable is present (it will be hidden for security).
4. Verify Disk Usage – In the project console run df -h to see the available space. Excessive local writes should keep this value well above the project’s quota limit.

Common Pitfalls to Avoid

• Storing Secrets Locally – Never commit API keys or passwords to regular files. Always use the .env mechanism.
• Excessive Local Writes – Large file writes can quickly exhaust the disk quota, causing the project to become read‑only or crash.
• Assuming Persistence – Files written by the running process may appear to work initially but disappear after a sleep or container restart.
• Ignoring Sleep Latency – Plan for a 1‑3 second delay on the first request after inactivity; cache warm‑up logic can mitigate user‑visible impact.

Practical Verification Steps

Run this minimal test to see the difference between local and external storage:

1. Create a new Glitch project.
2. Add the following code to server.js:

const fs = require('fs');
fs.writeFile('test.txt', 'Created at: ' + new Date(), () => {
  console.log('File written');
});

3. Restart the project from the settings panel.
4. Open the file explorer on the left; verify whether test.txt still exists.
5. Now add a simple MongoDB write (using the db.js example) and repeat the restart test. The document should remain in the database even after the restart.

Conclusion

The ephemeral nature of Glitch’s file system is a fundamental constraint that shapes your application architecture. For any data that must survive beyond a single container lifecycle, external storage is not just recommended—it’s essential. The initial setup complexity pays dividends in reliability, peace of mind, and scalability as your application grows.