MongoDB vs CockroachDB for Solo Developers

Quick Comparison

MongoDB Overview

MongoDB is the world's most popular document database. You store data as flexible JSON-like documents, which means no rigid schema to define upfront. For quick prototyping, this is genuinely useful. You can change your data model without running migrations, and documents map naturally to JavaScript objects.

MongoDB Atlas provides a free tier with 512 MB of storage on a shared cluster. This is enough for prototyping and small applications. The Atlas dashboard handles monitoring, backups, and scaling. For solo developers who want a cloud database without thinking about infrastructure, Atlas is a solid option.

The document model works well for content management, event logs, and applications where data structures vary. It works less well when your data has strong relationships that benefit from SQL JOINs.

CockroachDB Overview

CockroachDB is a distributed SQL database built for applications that cannot afford downtime. It is PostgreSQL-compatible, automatically shards data across nodes, replicates everything for fault tolerance, and maintains strong consistency across regions. If a node crashes, the database keeps serving requests without manual intervention.

The technology is built for scale and reliability problems that large companies face. Multi-region deployments, automatic failover, horizontal scaling, and serializable isolation. These are serious engineering solutions to serious infrastructure challenges.

CockroachDB offers a free serverless tier for experimentation, but the dedicated tier starts at $295/month. The free tier has limitations on storage, compute, and throughput that make it suitable for testing but not for production applications with real traffic.

Key Differences

Target audience could not be more different. MongoDB is designed for developers who want flexible data storage. CockroachDB is designed for organizations that need globally distributed, strongly consistent SQL. A solo developer building a SaaS does not need either of those at their extremes. But between the two, MongoDB's simplicity is far more appropriate.

SQL vs document queries. CockroachDB uses PostgreSQL-compatible SQL. MongoDB uses its own query language with find() and aggregation pipelines. SQL is more widely known, more powerful for relational queries, and supported by more tools. But CockroachDB's SQL comes with the overhead of distributed transactions, which adds latency. MongoDB's queries against a local replica are faster for simple operations.

Free tier comparison. MongoDB Atlas free tier (512 MB, shared cluster) is practical for small applications. CockroachDB's free serverless tier works for testing and learning, but the resource limits mean you will hit walls quickly with a real application. For budget-constrained solo developers, MongoDB's free tier is more usable.

Operational complexity. MongoDB Atlas is relatively simple to manage. Create a cluster, connect your app, query your data. CockroachDB introduces concepts like regions, survival zones, locality-optimized queries, and distributed transaction semantics. Even in its serverless form, CockroachDB asks you to think about distributed systems concepts that are irrelevant for most solo developer projects.

Data consistency. CockroachDB provides serializable isolation across distributed nodes, the strongest consistency guarantee available. MongoDB provides tunable consistency, from eventual to strong, but the default is eventual consistency for reads. For financial applications or systems where data accuracy is critical, CockroachDB's consistency guarantees are meaningful. For a blog, SaaS, or marketplace, both provide sufficient consistency.

Scaling path. MongoDB scales horizontally through sharding, and the process is relatively well-documented. CockroachDB scales horizontally by default, with automatic sharding built into its architecture. But again, a solo developer rarely needs horizontal scaling. A single PostgreSQL or MongoDB instance handles millions of rows efficiently.

When to Choose MongoDB

• You want a free tier for prototyping and small applications
• Your data fits the document model naturally
• You prefer flexible schemas over rigid table definitions
• You value simplicity in database management
• Budget is a primary constraint

When to Choose CockroachDB

• You need distributed SQL with strong consistency guarantees
• Multi-region deployment is a hard business requirement
• Automatic failover and zero-downtime operations are essential
• You need PostgreSQL compatibility with horizontal scaling built in
• You have the budget for enterprise-grade infrastructure

The Verdict

MongoDB wins for solo developers, and the decision is straightforward. The 7/10 vs 4/10 rating reflects a simple reality: CockroachDB solves distributed systems problems that solo developers do not have. It is an impressive technology, but the complexity and cost are aimed at teams running globally distributed applications.

MongoDB's free Atlas tier, simpler data model, and lower operational overhead make it the practical choice between these two. But if you are choosing a database for a new project as a solo developer, consider whether PostgreSQL (via Supabase or Neon) would serve you even better than MongoDB. Relational databases handle most web application data more naturally, and the managed PostgreSQL options are excellent.