In today’s rapidly evolving digital landscape, agility, scalability, and resilience are paramount for business success. Many organizations are transitioning from monolithic architectures to microservices to meet these demands. This shift, while rewarding, requires careful planning and execution. 

This blog post will explore the why, what, and how of transitioning from a monolithic to a microservices architecture. We will also share our experience in modernizing one of our enterprise applications by transitioning it from a monolithic architecture to a microservices-based architecture.

The transition from a monolithic to a microservices architecture is often driven by the need for greater scalability, flexibility, and speed. Some common reasons for making this shift include:

• Scalability: As your application grows, it becomes challenging to scale a monolith efficiently. Microservices allow you to scale only the parts of the application that need more resources.
• Faster Development Cycles: Microservices enable different teams to work on different services independently, speeding up development and deployment times.
• Resilience: Microservices can improve the fault tolerance of an application, as issues in one service are less likely to impact the entire system.

Monolithic Architecture.

A monolithic architecture is a traditional way of building applications as a single, unified unit. In a monolithic application, all components and functionalities—such as user interfaces, data access, and business logic—are tightly coupled and operate as a single entity.

Read more about monolithic: https://cloud.google.com/architecture/microservices-architecture-introduction#monolithic_applications

What Are Microservices? 

Microservices architecture is an approach where an application is built as a collection of loosely coupled, independently deployable services. Each service is responsible for a specific piece of business functionality and can be developed, deployed, and scaled independently.

Read more about microservices: https://cloud.google.com/architecture/microservices-architecture-introduction#microservices-based_applications

Steps to Transition from Monolithic to Microservices

Transitioning to microservices is not a one-size-fits-all process. However, the following steps can guide your journey:

1. Assess and Plan

Evaluate your current system to identify pain points in your monolithic architecture and determine if microservices are the right solution. Set clear objectives for what you want to achieve with microservices, such as improved performance, scalability, resilience, or faster release cycles. Develop a roadmap for gradually breaking down your monolith into microservices.

How we did it: In one of our enterprise products which was a monolithic application,  the client faced scaling issues as there were certain sets of API calls that were exposed to its channel partners and had heavy usage. This led to significant memory spikes on the EC2 instance, ultimately affecting the entire application’s performance. The API gateway was limited to 100 requests per second with a burst capacity of 20 in order to limit the concurrency. Simply increasing the rate limit and scaling the whole application to accommodate a few heavily used APIs wasn’t an ideal solution. Thus,  we created a plan to separate these heavily used external APIs and containerize these as individual microservices to enable independent evolution and autoscaling without impacting other resources.

2. Design Microservices

Determine the right level of granularity for each service—too coarse, and you lose the benefits; too fine, and you increase complexity. Decide how services will communicate (e.g., synchronous REST, asynchronous messaging). Define how data will be stored, accessed, and shared between services. Consider using databases per service. Create sufficient isolation to allow system room to evolve. Isolation could be at process level, network level and data level.

Here are a few important considerations for the design phase.

• Identify natural domain boundaries and protect them with APIs.
• Structure Microservices as independent applications that expose APIs, typically via REST or asynchronous event-driven mechanisms.
• Exclusive data ownership: Each domain must own its data exclusively, with access restricted to the respective microservice..
• Reduce dependencies and load on services providing APIs, enabling greater flexibility, easier client creation, innovative deployment strategies, and autoscaling.
• Isolate microservices by deploying them in separate containers or on different machines to prevent resource competition and break coupling.
• Contain failures within microservices, ensuring that only dependent services are impacted, not the entire system.

How we did it: We established boundaries in our application using domain boundaries. For example, when making a reservation, the resource and its availability for a particular time slot were crucial for verifying availability for both the resource and channel partner. We carved out an external-facing microservice for “reservation” and two helper microservices for “resource” and “channel partners”. For intercommunication with helper microservices, we implemented gRPC, which offers the benefit of low latency.

3. Decomposing the monolith

Decompose by Business capabilities

Break down the monolith by leveraging your organization’s business processes or capabilities that create value and generate revenue. Most organizations have multiple business capabilities, which vary by industry or sector. This approach works best if your team has a deep understanding of the business units.

How we did it: The diagram below illustrates the decomposition of our monolithic application into microservices, organized by business capabilities, such as Locations Management, Rates Management, Promotional, Reservations and Subscriptions(Monthly and Access Codes).