How to choose between microservices and monolith for enterprise software

The debate between microservices and monolith architectures is one of the most enduring in software engineering. While microservices are often touted as the modern, scalable solution, a poorly implemented microservices architecture can lead to significant operational overhead.

The Myth of "Microservices Default"

Over the last decade, there has been a strong industry push towards microservices. The narrative often suggests that if you aren't building microservices, you are building legacy software. This is fundamentally incorrect. A monolith is not a legacy pattern; it is a deployment pattern.

For most starting projects and even mature mid-sized businesses, a well-structured modular monolith is far superior. It reduces deployment complexity, eliminates network latency between services, and simplifies transactions and state management.

When to Choose a Monolith

• You are optimizing for speed of feature delivery: When all code runs in the same process, refactoring is simple. You don't have to coordinate deployments across teams.
• Your team size is small: If your engineering team is under 30 developers, the communication overhead of microservices will slow you down more than the architecture will speed you up.
• Strict data consistency is required: Monoliths allow for simple ACID database transactions. Managing distributed transactions across microservices requires complex patterns like Saga or two-phase commits.

When to Transition to Microservices

Microservices solve organizational scaling problems, not just technical ones. You should consider moving to microservices when:

• Independent deployment cycles are necessary: When teams block each other from deploying because they are tied to a single release train.
• Specific scalability bottlenecks: If one specific part of your application (e.g., image processing) requires massively different scaling characteristics than the rest of your app.
• Varying technology needs: When a specific feature requires a language or framework that your monolith does not support natively (e.g., Python for machine learning tasks within a Node.js ecosystem).

The Kirtav Approach

We strongly advocate for starting with a Modular Monolith. Build boundaries inside your codebase without creating network boundaries. By using domain-driven design, you enforce clean separation of concerns. If and when a module needs to be extracted into a microservice, the boundaries are already well-defined, making the transition seamless and risk-free.