Monolith vs microservices: what actually matters

Most businesses don’t start by choosing between a monolith and microservices.

They start with something that works. Then over time, that system becomes harder to change, slower to deploy, and increasingly fragile.

At some point, the question comes up: Do we need to move to microservices? A fair question. But it’s also the wrong place to start.

What is a monolith?

A monolithic architecture combines all components into a single, unified application and deploys them together with tight connections.

That means:

• One codebase

• One deployment process

• Often one shared database

For many businesses, this works well, especially early on.

Monoliths are:

• Simpler to build

• Easier to test

• Faster to get to market

The problem isn’t the monolith itself, it’s what happens as it grows.

What are microservices?

Microservices divide an application into small, self-contained services, each responsible for one specific function.

For example:

• User management

• Payments

• Orders

• Reporting

Each service:

• Can be deployed independently

• Can scale independently

• Communicates with others via APIs

In theory, this creates more flexibility and scalability. In practice, it introduces a new kind of complexity.

The real difference 

This isn’t about architecture patterns. This is about how your business operates.

• Monoliths optimise for simplicity

• Microservices optimise for flexibility

The right choice depends on:

• How fast you need to change

• How many teams are involved

• How complex your system has become

When a monolith is actually the better choice

Microservices are often seen as the “modern” option but that doesn’t mean they’re always the right one. A monolith is often better when:

• Your product is still evolving

• You have a small team

• Your system isn’t hitting scaling limits

• Speed of development matters more than flexibility

In many cases, moving too early to microservices creates more problems than it solves.

When microservices start making sense

Microservices become valuable when your system reaches a certain level of complexity.

For example:

• Multiple teams need to work independently

• Deployments are slow or risky

• Different parts of the system need to scale differently

• Changes in one area regularly break others

At this point, the architecture starts to reflect organisational needs.

Why most monolith-to-microservices projects fail

This is where things usually go wrong. Many businesses assume: “If we move to microservices, everything will improve”

But in reality:

• Poor architecture doesn’t disappear - it gets distributed

• Complexity increases significantly

• Communication between services becomes a challenge

• Data consistency becomes harder to manage

The biggest issue: Teams focus on technology decisions instead of business outcomes

A better approach to modernisation 

Rather than asking: “Should we move to microservices?”

A better question is: “Where are the bottlenecks in our system and how do we remove them?”

In practice, modernisation usually looks like:

• Understanding where systems are slowing the business down

• Gradually separating high-impact areas

• Introducing new architecture patterns where they add value

• Avoiding large, high-risk rewrites

This is often called an incremental approach. It sometimes uses patterns like the “strangler” approach. This replaces parts of a system over time.

Microservices won’t fix your business problems

This is worth being clear about. Microservices don’t:

• Improve poor processes

• Fix unclear requirements

• Replace the need for good data

• Automatically make systems scalable

What they can do is support a business that:

• Needs to move faster

• Operates at scale

• Requires real-time decision-making

What actually matters

Instead of focusing on architecture trends, focus on outcomes:

• How quickly can you make changes?

• How reliable are your systems?

• How easy is it to scale?

• How confident are your teams in deploying updates?

Architecture should support these, not drive them.

If you’re thinking about modernising your systems, it’s worth stepping back before making major architectural decisions.

In many cases, the answer isn’t a full rebuild. It’s a more practical, step-by-step approach. It lowers risk while still moving things forward.

If you’re working through this, we’re happy to share an honest view. Even if the best choice is to keep things as they are.