Understanding Modular Monolith
A Modular Monolith keeps a single codebase and deployment but divides the system into modules. Each module has clear responsibilities, boundaries, and interfaces.
“A modular monolith allows small teams to scale code structure without overcomplicating deployments.”
— Viswa
— Viswa
Key Principles
- Divide the code into modules based on functionality (e.g., user, orders, inventory).
- Modules should communicate through defined interfaces or APIs within the monolith.
- Keep one deployable unit to simplify operations.
Pros & Cons
- Pros: Easier deployment, clear modular structure, faster to develop than microservices for small teams.
- Cons: Modules can become tightly coupled over time, scaling large teams may eventually require microservices.
Real-World Examples
- Growing SaaS applications before splitting into microservices.
- E-commerce platforms with separate modules for catalog, orders, and payments.
- Internal business apps where teams share a single deployment pipeline.
Common Failure Modes
- Modules sharing internal data structures directly instead of interfaces.
- Team changes accidentally breaking other modules.
- Overloading modules with too many responsibilities, losing modularity.
When to Use
- Small to medium teams that need modularity but cannot manage microservices.
- Projects requiring fast iteration without operational overhead.
- When deployment simplicity is more important than absolute scalability.