Migrating from Monolith to Microservices

Monolithic applications, characterized by their unified and interconnected structure, face challenges such as scalability bottlenecks and hindered development speed. 

The evolution of microservices architecture is examined, shedding light on its inherent advantages, such as improved scalability, fault isolation, and accelerated development cycles. As organizations increasingly recognize the transformative potential of microservices, the need for a strategic approach to migration becomes apparent. The upcoming segments unfold a comprehensive plan encompassing assessment, planning, and the intricate process of breaking down the monolith into modular and loosely coupled microservices components. This exploration serves as a foundational guide for organizations poised to embark on the path of modernizing their application infrastructure.

Why Should You Migrate to Microservices?


Traditionally, software applications were constructed as monolithic entities, encapsulating all functionalities within a single, mammoth codebase. This approach, while functional, posed challenges as applications grew in complexity. The tightly coupled nature of monoliths made it cumbersome to update, scale, or innovate without risking cascading effects throughout the entire system.

Business Flexibility

Microservices architecture emphasizes bounded context between its independent components, making your system easily modifiable. Adding, removing, and upgrading features based on your business needs takes much less effort. So, it’s easier to keep systems relevant and competitive.

Faster Deployment

Microservices code is more understandable since it’s restricted to a single data repository. Your teams will get the dependencies and know what to expect when modifying the codebase. It makes testing more consistent and coherent, saving you time and money on upgrading the system.

Productive Environment

Defined boundaries and minimal dependencies allow teams to implement, scale, and deploy multiple microservices simultaneously. It also implies your developers have more autonomy. For example, they can choose programming languages, frameworks, and APIs better suited to their goals, improving their productivity.

Fault Tolerance

Modification in one module can break the entire monolith application, but things are the other way around in loosely coupled architecture. Each microservice isolates its code errors and limits their impact on the system. It means that migrating from monolith to microservices makes your system more tolerant of failures.


Companies can scale microservices in isolation based on their needs without affecting the rest of the application. What does this mean? You can improve performance for specific software modules by scaling computing resources up or down.

Cost Savings

Microservices enable you to update or patch individual services without disrupting the entire application. Because services are smaller and more isolated, it’s easier to identify and fix issues. Also, you don’t need to scale the entire application during peak usage. This way, you optimize resource allocation, reduce downtime, and avoid unnecessary costs.

What big company has already switched from a monolithic application to microservices? We will tell the stories of three giants:

  • Netflix’s monolithic architecture quickly became ineffective as its user base grew rapidly. The company has made the transition as smooth as possible to maintain a good user experience. Starting with separating server services, Netflix gradually moved to features such as registration, settings, movie selection, etc. A microservice architecture helps the company ensure the platform’s stability and performance during peak periods.
  • Previously, Amazon had a two-tier structure. But with the introduction of new features and the growth of the code base, development and deployment took too much time. With the move to a microservice architecture, all functions could be updated independently because the functions communicated through their web service APIs. It also helped the company grow into the world’s largest e-commerce market and withstand heavy server loads.
  • Uber was created as a one-city service located in San Francisco. The main functionality was concentrated in a single codebase: communication between drivers and passengers, invoicing, and payments. With service scaling and continuous integrations, the company moved to a microservice architecture to not rely on dependencies between application components.

Unleash the Power of Microservices with Ardas

Just as Netflix, Amazon, and Uber successfully transitioned to microservices to enhance growth and system performance, Ardas specializes in developing robust SaaS products that help businesses scale efficiently and tackle complex challenges with expertise in software architecture.

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When You Shouldn’t Refactor Monolith to Microservices

Microservices solve many problems that monolith applications have. Yet, they aren’t a silver bullet for everyone:

  • Microservices come with a high initial cost. Moving to loosely-coupled architecture requires significant investments in infrastructure building, documentation development, and application refactoring. You also need to allocate resources and storage space for every service, which can eat up the IT budget.
  • You need experienced staff. Microservices require a professional team that knows how to work in distributed environments. You must also implement automated development and DevOps practices to maximize productivity in microservice systems.
  • Challenges of distributed systems. Loosely coupled services communicate through APIs. Your architects and developers should factor in latency, network topology, security, bandwidth limits, and other transport costs.

These problems demonstrate that microservice web app architecture isn’t always beneficial for startups and midsized companies. This allows multiple departments to work on different products simultaneously. By setting boundaries for different components, you can divide these modules into fully independent microservices when the time comes.

Choosing the Strategy to Migrate Monolith to Microservices

A migration strategy will help you move the applications with minimal errors.

Begin by assessing the large-scale structure of your monolith system and identity functionality.

Group functionality into bounded contexts — sets of closely related features and business functions. For example, you can put customer loyalty, user rating, and account functionality into the “account” context, while drone sharing, predictive analysis, and drone repair will become the “drone management” group.

Specify features you want to migrate and prioritize first-movers. Then, you can remove dependencies between the bounded contexts and isolate them into separate modules. Here are the two most popular approaches:

  • Parallel adoption. This technique means moving functionalities to the new system without shutting down the old one. Running duplicate features in parallel helps you compare their behavior to validate that the new application works as expected.
  • Phased adoption. In this approach, you move selected features to microservices, leaving some functionality in the monolith system. This helps evaluate the quality of solutions and isolate errors in smaller parts of the system. Read more about microservice migration.

Pick the one that suits your organization’s structure, migration scope, and business goals. In some cases, combining the approaches can yield even better results.

Microservice Migration: A Step-by-Step Guide

We prepared this monolithic to microservices migration strategy to help you avoid compatibility errors and performance issues (if you don’t want to use IT outsourcing).

Step 1: Assess Readiness for Migration

A successful migration requires analyzing the current infrastructure, internal policies, and team competence. Some of the points needing your attention include:

  • Core business priorities. Determine what you want to gain after moving to microservices. It could be rapid development, increased uptime, innovation, or scalability.
  • Service-level agreements. Make sure the SLAs align with various components of the deployment infrastructure. You also need to understand the SLAs of cloud providers if you wish to host the application on serverless platforms.
  • Team structure. Microservices require effective communications and autonomy from teams. It means you must assess the tools for collaboration and a governance model in your organization.
  • Infrastructure readiness. The loosely-coupled architecture allows you to shorten your release cycles to bring more value to customers. So, consider what tools and methods you use to deploy services and how you can remediate them after failed deployments.
  • DevOps competence. Your teams should understand the fundamental practices of DevOps and have the right tech to maximize organizational agility in microservices.
  • Security measures. Cybersecurity is critical for microservices architecture, and you must consider it for every isolated system. Assess your authorization and authentication measures, API gateways, communication protocols, network security protocols, and firewalls.

The assessment lets you understand what areas of your company need improvements before you can start identifying features to migrate.

Step 2: Identify Functions and Dependencies

Code often piles up in monolithic architectures, making it too complex and full of hidden dependencies. For example, code for a payment service can go to external payment providers, load irrelevant libraries, or hit retired processes.

Start by inventorying your functions and business capabilities. Each microservice must serve a specific function and have a single data repository. So, you must retire applications that duplicate each other’s functionality or provide similar data from multiple locations.

Step 3: Select Migration Candidates

Determine which bounded contexts (functional groups) provide the most value as microservices and which you should leave in the monolith system for now.

The developers will give you insights into the existing implementations, dependencies, and internal events. The non-technical experts will tell you about things missing in your services or features that might be critical in the future.

For example, a payment service group should include payment authorization, refund, cancellation, and status check modules. You might exclude related services with different domain areas, like order status, inventory check, and package tracking.

Step 4: Prioritize Services for Migration

You need to identify components to move first. Start with edge services — bounded contexts with fewer dependencies that are likely to be easiest to decompose into smaller services. These could include order management, invoicing, or notification features.

You might also migrate monolith to microservices to address problems like performance bottlenecks.

Step 5: Select a Scalable Infrastructure

You can use certified cloud providers like Google Cloud, Microsoft Azure, and Amazon Web Services.

They let you easily scale resources for microservices and even support autoscaling. Flexible pay-as-you-go billing means you don’t pay for the resources you don’t use. You also get secure communication protocols and authorization tools to safeguard your corporate data. Additionally, the providers take care of the infrastructure maintenance for you.

Step 6: Separate the Application’s Layers

When migrating to microservices, you must separate your monolithic applications' presentation, business logic, and persistence (data) layers.

As you divide the layers, you must set up gateway APIs that route requests between the client and the backend. The API sets the boundaries between layers, helping your teams decouple and isolate the application. It also deals with cross-cutting tasks like SSL termination, authentication, and rate-limiting.

Step 7: Set Up Communications

Effective communication ensures exchange between different services in the loosely coupled architecture. The primary messaging patterns include synchronous communication (where the caller waits for a response) and asynchronous messaging (the service can send multiple messages simultaneously). We recommend switching to asynchronous as you move more applications to microservices.

Your team must also set up appropriate public APIs (for client application calls) and backend APIs (for interservice communication). A public API should be compatible with your mobile and web applications. When selecting an API for the backend, you must factor in latency, network performance, and payload size.

REST over HTTP/HTTPS is usually the optimal pattern for the client side. As for the server side, your options include RESTful interfaces (focused on stateless communications and scalability) and RCP interfaces (oriented towards commands and operations).

Step 8: Migrate Data

The next step includes moving legacy databases, logic, and behaviors that support the application.

Some applications will also need to access old data from your monolith (primarily in a phased adoption approach). You need to configure an API to gather information from other services. This way, the payment microservice can fetch data from the profile module in the monolith.

Step 9: Create a CI/CD Pipeline

Without well-oiled continuous integration (CI) and continuous delivery (CD) processes, you won't get the most out of the new architecture. The CI allows your team to test changes to always keep the code production quality automatically. CD tools help your teams automatically publish the code changes to the production environment.

Step 10: Implement and Deploy

Deploy the functionality gradually to ensure everything works as expected in the new architecture. Unfortunately, you might identify a significant semantic difference between the legacy and new systems. Here’s how you can solve these problems.

Use an anti-corruption pattern (glue code) — a layer that translates communication between the existing monolith and a new system. It helps you transfer only the data the microservice requires, basically filtering unnecessary data that might pollute your system.
The canary release technique can help you reduce performance issues and errors when moving from monolith to microservices. Let’s say you migrated the application with a phased approach. First, send the traffic to the new microservice to a limited number of users (5%). If there are no errors, you can progressively increase the user count up to 100% before switching fully to a microservice.

After refactoring the application into a consistent microservice, you can remove the glue code and retire the monolith components. Then, rinse and repeat until everything becomes your scalable architecture.


Migrating from monolith to microservices is inevitable for growing companies industry-wide. The traditional monolithic architecture doesn’t provide the scalability, flexibility, and efficiency their teams need.

Migrating monolith to microservices challenges can be scary, especially for outdated systems and unorganized legacy code. Luckily, we at Ardas have the expertise and over a hundred cloud migrations to assist you.

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