MongoDB vs Firebase for Solo Developers

Quick Comparison

MongoDB Overview

MongoDB is the most popular document database. It stores data as JSON-like documents, supports flexible schemas, and scales horizontally. MongoDB Atlas provides a managed cloud platform with a free tier that works for small applications.

For solo developers, MongoDB is familiar territory if you work with JavaScript. Documents map naturally to JavaScript objects. Mongoose (the most popular ODM) provides schema validation, middleware, and query building. The ecosystem is mature with years of community support.

MongoDB gives you more control than Firebase. You can self-host it, run complex aggregation pipelines, define your own API structure, and optimize queries with custom indexes. This flexibility is valuable when your application has specific data access patterns.

Firebase Overview

Firebase is Google's application development platform. At its core is Firestore, a NoSQL document database with real-time synchronization built in. But Firebase is much more than a database. It includes authentication, cloud storage, hosting, cloud functions, analytics, and crash reporting.

The appeal for solo developers is speed. Firebase lets you build a functional application incredibly fast. Set up Firestore, enable authentication, deploy to Firebase Hosting, and you have a live application. The real-time sync means your UI updates instantly when data changes, without writing WebSocket code.

Firebase's free Spark plan is generous. Firestore gives you 1 GB storage, 50,000 reads, 20,000 writes, and 20,000 deletes per day. That handles most prototypes and small applications without spending anything.

Key Differences

Platform vs database. Firebase is a complete application platform. MongoDB Atlas is primarily a database (though Atlas App Services add some platform features). For a solo developer, Firebase's bundled services mean less integration work. Auth, storage, and hosting are all configured from one console. With MongoDB, you piece together these services individually.

Real-time architecture. Firebase was built for real-time from day one. When you write data to Firestore, every client subscribed to that data gets an update instantly. MongoDB has Change Streams for real-time data, but you need to set up your own WebSocket server to push updates to clients. For chat apps, collaborative features, or live dashboards, Firebase's real-time is easier to implement.

Querying limitations. This is where Firebase frustrates people. Firestore queries are limited. You cannot do inequality filters on multiple fields. JOINs do not exist. Complex queries require workarounds like denormalized data or composite indexes that you must create manually. MongoDB's aggregation pipeline is more powerful and flexible for complex data operations.

Pricing predictability. Firebase charges per document read, write, and delete. This can spike unpredictably. A poorly optimized query that scans thousands of documents costs real money. MongoDB Atlas has more predictable pricing with its shared and dedicated cluster tiers. For solo developers, Firebase's pay-per-operation model can produce surprise bills if you are not careful.

Vendor lock-in. Firebase locks you into Google Cloud. Your data, auth, hosting, and functions all live in Google's ecosystem. Migrating away means rewriting significant portions of your application. MongoDB Atlas has some lock-in to the Atlas platform, but the underlying MongoDB database is open source and portable. You can self-host MongoDB if needed.

Offline support. Firebase has excellent offline support. Your app continues to work when the network drops, and data syncs when connectivity returns. This is especially valuable for mobile apps. MongoDB does not have built-in offline support for client applications (you would need MongoDB Realm for that).

When to Choose MongoDB

• You need complex queries that Firestore cannot handle
• You want to avoid Google vendor lock-in
• Your data access patterns require aggregation pipelines
• You prefer a database you can self-host if needed
• You are building a backend API that serves multiple clients

When to Choose Firebase

• You want the fastest path to a working application
• Real-time data sync is central to your app
• You are building a mobile app that needs offline support
• Auth, storage, and hosting in one platform saves you time
• Your queries are simple (lookups by ID, simple filters)

The Verdict

Firebase is the better pick for solo developers building their first product or prototyping quickly. The 8/10 vs 7/10 reflects the time savings from having auth, real-time, storage, and hosting bundled together. You can go from idea to live application in a weekend.

MongoDB is the better pick when your data needs outgrow Firebase's querying limitations. If you need complex aggregations, flexible indexing, or prefer building your own backend, MongoDB gives you more control.

My recommendation: start with Firebase for speed. If your querying needs become complex, consider migrating to Supabase (PostgreSQL) rather than MongoDB, since you will likely want relational data modeling at that point. MongoDB occupies a middle ground where Firebase is simpler and PostgreSQL is more powerful. For solo developers, going to one extreme or the other usually serves you better.