Monolith vs. Microservices: The Differences and How to Evolve

A few years ago, I wrote about how software is vital to remain competitive. Yet this statement isn’t exactly true anymore. Most companies have adopted new software or built custom applications to streamline their processes, reach higher efficiency, and improve customer satisfaction.

A few years ago, I wrote about how software is vital to remain competitive. Yet this statement isn’t exactly true anymore. Most companies have adopted new software or built custom applications to streamline their processes, reach higher efficiency, and improve customer satisfaction.

Therefore, we’re seeing a new trend focusing on providing faster, better, and more reliable services to further improve the company’s efficiency and the end-user experience.

For that reason, many organizations shift from a traditional monolith architecture to a microservices architecture.

What exactly is a microservices architecture, and how do you migrate to such an architecture? This article answers these questions.

First, let’s explore the differences between monolith and microservices architectures.

A large and small box signifying microservices vs. monolith

What’s the Difference Between Monolith and Microservices?

Microservices architecture is the same as a monolith architecture but broken down into smaller pieces.

A monolith architecture contains all code in a single repository. This structure is often problematic as it becomes increasingly more challenging to maintain or update the code. As a side effect of monolithic architecture, components get interlinked and are hard to decouple. As a result, it’s not easy to scale individual components. Therefore, you can only scale the whole application, which can become very costly.

For that reason, a microservices architecture breaks down a monolithic architecture into stand-alone components. Each component has a single responsibility and is decoupled from others. It’s much easier to scale components individually. On top of that, adding new functionality becomes much easier.

Let’s discuss a webshop use case to better understand a microservices architecture. Imagine a monolithic webshop that contains the following components:

  • Retrieve product data and look up product availability
  • Process payments
  • Store client information

Now, a lot of users look up products. Therefore, the webshop has to scale to handle the high amount of traffic. Scaling a monolith is quite costly as you can’t simply scale the product retrieval component but have to scale the whole application.

Therefore, a microservices architecture breaks up the different components to scale components individually based on the demand.

Reasons to Switch to a Microservices Architecture

Next, let’s discuss different reasons to switch to a microservices architecture. Here are the three most prominent reasons to switch.

1. Increased Code Maintenance and Avoiding Code Duplication

A microservices architecture prevents code duplication. By decoupling components, you create a modular architecture that allows you to quickly develop new applications reusing existing services.

Let’s say you have a service that stores and retrieves customer data. You’ve integrated this service in your webshop. Further, you decide to develop an internal application for looking up customer information or generating customer reports. Therefore, you can reuse this existing service for your internal application.

Create a modular architecture that allows you to quickly develop new applications reusing existing services

2. Reduced Technical Depth

While microservices provide many benefits for your organization, they also benefit developers. It’s much easier for developers to learn about stand-alone services and understand their functioning.

On the other hand, a monolithic application is often far more complex and requires significantly more time to understand. Monolithic applications are often the primary source of technical debt among developer teams. As part of a developer team, you want to avoid technical debt as it slows down your team and the company’s time to market.

3. Improved Reliability

When switching to a microservices architecture, you improve the reliability of the services.

A single failure within a monolithic architecture can cause your entire application to crash. For instance, an uncaptured exception in your payment processing component can fall through and crash your entire application. This behavior hurts your services’ reliability.

A microservices architecture improves reliability as exceptions can’t fall through to other services. Therefore, only a single component fails without affecting the availability of other critical services.

How to Evolve to a Microservices Architecture

Here’s a step-by-step guide to help you migrate from a monolithic architecture to a microservices architecture.

Step 1: Define Domains

Start by defining the different domains for your application. By understanding the different domains in your application, you can decouple components more quickly.

For example, a webshop has the following domains:

  • Payments
  • Customer data
  • Product data

This strategy allows you to define services that have a single responsibility and fit a particular domain. You want to avoid cross-domain services as this leads to coupled services.

Step 2: Decouple Sticky Components

In the previous step, we’ve defined the different domains for your application. This definition gives you more insights into components that are most sticky. In other words, components that span two or more domains.

It’s essential to start with sticky components. If you start with easy-to-decouple components, you’ll find that it’s hard to truly decouple them from your monolithic architecture. Therefore, start with the most coupled components, which allows you to quickly decouple other components as they all interact with this poorly designed component.

Step 3: Build a Continuous Integration (CI) Pipeline

When you’ve decoupled some of your crucial services, it’s time to set up your CI pipeline. This pipeline allows your development team to adopt the agile development methodology and integrate automated testing.

A well-configured CI pipeline will improve your team’s productivity and increase code quality via automated testing. Moreover, microservices support parallel development. To reap the full benefits of parallel development, you require a CI pipeline to handle builds and testing asynchronously.

Step 4: Use Monitoring and Logging Tools

As a final step, let’s take a look at monitoring and logging tools. A disadvantage of implementing a microservices architecture is the increased difficulty to measure performance and gain visibility.

Thus, setting up monitoring tools is essential to gain visibility into your different components’ performance and scale effectively.

On top of that, you’ll have to look for a log aggregation tool as each microservice generates logs. Companies often find that their log data volume explodes. As a result, companies tend to throttle down the amount of log data they store, opting instead for metrics rather than context.

Consequently, it becomes harder for developers to debug user requests as a request passes multiple services. For that reason, a log aggregation tool such as Scalyr improves visibility and aggregates logs for all your microservices. On top of that, Scalyr makes it really efficient to search logs and get results with context.

improve your team's productivity and increase code quality via automated testing

Should You Migrate to Microservices?

While it sounds very appealing to migrate to a microservices architecture, make sure your company is ready for this change. First of all, you require developers capable of leading this impactful transformation. Preferably, hire developers who have experience with the migration process to microservices.

On top of that, you’ll have to design a strategy to maintain your monolith while slowly deprecating components that you’ve migrated. Don’t underestimate this.

Lastly, many developers assume they’re done when they’ve decoupled all monolith components into reusable services. However, this is where the journey begins. Configuring a continuous integration and continuous delivery pipeline is also essential, not to mention installing a log aggregation tool or monitoring tool.

Most developers don’t realize that a microservices architecture comes with different problems, such as distributed logs, that require a solution. Therefore, there’s a strong focus on the DevOps aspects when migrating to a microservices architecture. Make sure your DevOps team is ready for this change.

As a bonus tip, make sure to document all steps. It’ll help you to share knowledge among developers and help them understand how domains work. You don’t want to end up with microservices that perform multiple functions, creating extra complexity.

This post was written by Michiel Mulders. Michiel is a passionate blockchain developer who loves writing technical content. Besides that, he loves learning about marketing, UX psychology, and entrepreneurship. When he’s not writing, he’s probably enjoying a Belgian beer!