From Monolith to Microservices Architecture - Common Pitfalls and how to avoid them

Introduction 

Microservices is not just a buzzword, it has revolutionized how software applications are built. You may not start your application development with microservices architecture, but you will be migrating to it sooner or later. As microservices are slightly complex compared to traditional monolith architecture, many teams struggle during this migration phase. That is exactly the problem we are going to solve today. This article will go through different challenges faced during migration from a monolith to a microservices architecture. Of course, migrating from monolith to microservices is more challenging than starting with microservices from scratch. In this article, we will not only discuss different issues when moving to microservices but will also share some best practices that will simplify this migration journey. Let’s start with understanding both architectures in detail. 

Understanding Monoliths and Microservices 

Monolithic Architecture

A monolithic architecture is a software design pattern where all components of the application (user interface, business logic, and data access code) are tightly coupled and run in a single process. This architecture is simple to develop, test, and deploy as it’s a single, autonomous unit. However, it can become complex and difficult to manage as the application grows. If you are unsure whether you should use monolith architecture or microservices, read our previous article on the same topic https://vizzon.co.uk/microservices-vs-monolith-which-architecture-to-choose/ 

Microservices Architecture

On the other hand, a microservices architecture breaks down the application into small, loosely coupled services, each running in its own process and communicating with others via APIs. Each microservice is responsible for a specific business capability, can be developed and deployed independently, and can be scaled individually. This architecture provides flexibility, scalability, and resilience, but it also introduces complexity in terms of service coordination and data consistency.

Why Migrate from Monolith to Microservices?

Organizations consider migrating from monolith to microservices for several reasons:

Scalability

Microservices can be individually scaled based on demand, making the system more responsive and cost-effective.

Resilience

Failure in one microservice doesn’t affect the entire system, improving the overall uptime and user experience.

Faster Time-to-Market

Independent development and deployment of microservices enable faster feature releases and bug fixes.

Technological Freedom

Each microservice can use the technology stack that best suits its requirements, fostering innovation and efficiency.

Common Pitfalls During Migration

Pitfall 1: Lack of a well-defined bounded context

In the context of microservices, a bounded context is a specific responsibility or a function that a service performs. When migrating from a monolith to microservices, it’s crucial to properly define these contexts. Failing to do so can lead to services that are tightly coupled or have overlapping responsibilities, negating many of the benefits of a microservices architecture.

Example: Consider an e-commerce application. If you migrate without properly defining the boundaries between user management, inventory, and payment services, you may end up with services that are not truly independent, complicating the development and deployment process.

Pitfall 2: Improper service granularity

The size of your services, or their granularity, is another important consideration. Services that are too large may not offer much improvement over a monolithic architecture, while services that are too small (nanoservices) can lead to communication overhead and make the system more difficult to manage.

Example: If you create too many small services without a clear rationale, you may end up with a system that is complex and difficult to manage, with a high degree of inter-service communication. Note that each microservice runs in its own process and memory which means the call from one microservice to another is a network call. If you compare it with a monolith application, then all modules/services are in the same memory and process, hence inter-service communication has no latency. 

Pitfall 3: Not handling data management challenges

Most of the applications, especially data-intensive applications need to share data and manage transactions across multiple microservices. Take the example of an e-commerce application where a payment microservice will need to share data with a shopping cart microservice. If you do not implement a proper mechanism to share data across different services you will face issues like inconsistent data, increased latency due to remote data access, and difficulties in managing transactions that span multiple services.

Pitfall 4: Overlooking team communication and coordination

Let’s assume a scenario where some of the microservices will be developed in one tech stack and by one team, while others will be in a different tech stack and by a different team. Some other microservices might be developed by a small team of domain-specific experts. Now all these teams will need to have close coordination with each other so that their respective services know how to talk to each other. Without clear communication and coordination protocols, teams can easily get out of sync which may lead to issues like conflicting changes, duplicated work, reduced team velocity, and integration problems

Best Practices for a Successful Migration

Now that we have gone through some of the critical challenges in microservices architecture, it’s time to go through some of the solutions that will solve these problems. Let’s go through these one by one:

1. Strangler Design Pattern

This is a potent technique when you want to migrate from monolith architecture to microservices architecture with zero downtime. This approach involves gradually replacing parts of the monolith with microservices. You can incrementally migrate functionality and reduce risk. Start by identifying a specific function of your monolith to replace, strangle it out by building a corresponding microservice, reroute the traffic to the new service, and repeat this process until the entire monolith is strangled. The below diagram illustrates the strangler design pattern.

 

                                    Source: https://microservices.io/refactoring/

2. Domain-Driven Design

Domain-driven design is a well-known strategy that involves defining well-bounded contexts for services based on the business domain. Each microservice should align with a specific business capability and be developed by a team that understands that domain. Take the example of an e-commerce application. The User Management microservice would encapsulate only the logic related to user management. It will expose an API for other services to interact with it. It would have its own database to store user data. Similarly, the product catalog microservice would manage all product-related data and operations. It would provide APIs for other services to search for products, get product details, etc.

3. One Database per Service

To ensure loose coupling, each microservice should have its own database. A shared database would not allow you to take full advantage of microservices. One database per service allows each service to manage its own data model and ensures data consistency within the service boundary. On the downside, it also introduces challenges in managing transactions and queries that span multiple services because of data sharing and transactions across multiple databases.

4. API Gateway

An API gateway is a server that acts as an entry point into your microservices ecosystem. It handles requests from clients, routes them to the appropriate microservices, and aggregates the responses. The API gateway can also handle cross-cutting concerns like authentication, rate limiting, and caching.

5. Continuous Integration/Continuous Deployment (CI/CD)

Implementing CI/CD pipelines for each service is crucial to ensure rapid and reliable deployment. Each microservice should have its own pipeline, allowing it to be built, tested, and deployed independently. For example, you might want to deploy just the payment microservice without needing to deploy other microservices. Having separate CI/CD for each microservice accelerates the feedback loop, reduces the risk of bugs reaching production, and enables faster recovery when issues do occur.

Conclusion 

Wow that was not that difficult, was it? If you have gone through this article, you will breeze through the migration from monolith to microservices easily. We discussed different challenges like data management, inter-service communication, etc. The best practices including different design patterns will help you solve these migration problems. Whether you are looking to implement microservices from scratch or migrate from monolith to microservices, Vizzon team can help you with the process. Our skilled team has extensive experience in migrating monolith enterprise applications to microservices-based applications. Contact us today to get more information on how we can help you cross this bridge easily.