Modular Monoliths: The Comeback Architecture

Why splitting too soon might break you — and how to build a clean, modular system in .NET

Microservices are sexy. They scale teams and tech.
But sometimes, a monolith — a modular monolith — is exactly what you need.

In this post, I’ll walk through:

• Why modular monoliths are making a comeback
• When you shouldn’t go microservices
• How to enforce boundaries inside a .NET monolith
• Real-world patterns and battle scars
• C# examples with InternalsVisibleTo, DI modules, ITenantService tricks, and more

The Theory

Microservices are not the goal

They’re a response to pain. Scaling pain. Deployment pain. Team coordination pain.

But what if you don’t have that pain — yet?

Jumping into microservices too early is like hiring HR before your first employee.

“You don’t start with a distributed system. You start with a monolith, and you carefully modularize it…”
— Martin Fowler, Monolith First

When a modular monolith wins?

• Early-stage startup: Faster to build, debug, deploy