Microservices vs. Monolithic Architecture: What Will You Choose?

One of the first and most critical steps in developing any software product or system is choosing the architecture for the future solution.

Monolithic architecture is a time-tested classic and a reliable approach to IT system development. In a monolithic architecture, the entire application is built as a single, unified unit. All components: the user interface, business logic, and data access layer, are tightly integrated and run as a single process. This architecture offers simplicity, ease of deployment, and better performance for smaller or simple systems. However, monolithic applications can become challenging to maintain and scale as they grow larger.

Microservices emerged as an innovative alternative, gaining popularity with the rise of distributed systems and the need for more flexible resource utilization. Unlike monolithic architecture, microservices break an application into a collection of smaller, independent services, each responsible for a specific functionality. These services communicate with each other through APIs, allowing for greater flexibility, scalability, and fault tolerance. Developers can deploy, update, and scale each service independently. However, this architecture also introduces complexity, such as the need for robust communication mechanisms, distributed data management, and monitoring across multiple services.

There was a period when microservices were the go-to choice for nearly every project, often favored simply because they were the trend of the day. While both architectures have their strengths and weaknesses, the choice between monolithic and microservices should depend on the specific needs and goals of the project rather than prevailing trends.

However, the development landscape evolves rapidly, and as trends fade, they give way to a balanced and pragmatic assessment of any technology or methodology. The modern approach focuses on efficiency, alignment with business processes, and the unique logic of the company for which the system is being built. Thus, the architecture of a software solution must ultimately aim to deliver the most effective outcomes, including:

• Streamlined development,

• Optimal system performance,

• Efficient resource utilization.

In this article, we’ll explore the pros and cons of monolithic and microservices architectures, their unique characteristics, and their ideal use cases. By understanding these factors, you’ll be equipped to make the best architectural choice for your system at the outset of development.

Monolithic Architecture

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Monolithic architecture assumes that all system components are interconnected, dependent on each other, and operate using a unified data storage system through a shared interface. For web applications, for instance, this means that the client-side and server-side parts of the system are elements of the same software project.

The distinguishing features of this architecture include:

• All project functionality is contained in a single repository and is often initially hosted on a single server.

• Typically, especially in the early stages of system development, a single database is used.

• Due to the interdependence of all components, changes to one part of the system usually result in modifications to other parts, necessitating their adjustment or potentially causing downtime.

• Deployment of such a system occurs as a single executable file that simultaneously launches all system parts.

From these characteristics, a logical set of advantages and disadvantages of this architecture emerges. Notably, at different stages of a system's lifecycle, advantages can turn into disadvantages.

Traditionally, the advantages of monolithic architecture include the following:

1. The simplicity of development and deployment: A unified system with a standardized set of internal rules, a single codebase, and shared business logic makes it straightforward to create and deploy the project.

2. Unified database: Since all system components interact with the same database and exchange data in a unified format, there is no need for additional synchronization mechanisms.

3. Ease and convenience of debugging: Thanks to internal standardization and the interconnection of all components, identifying and fixing issues within the system is faster and more straightforward.

4. Performance and efficiency: The unified system infrastructure and the seamless integration of all components minimize time delays for task execution, as everything operates within a single process.

5. Low deployment cost: Overheads for building a distributed system across multiple servers are reduced, as are expenses related to inter-server communication.

Now let’s consider the disadvantages of monolithic architecture:

1. Scalability: This is the most significant drawback of monolithic architecture. Any change or expansion of the system requires varying degrees of modification across all its components. As a result, even the smallest change can become a large-scale task.

2. Maintenance and updates: Over time, every system requires updates and modifications - the need to expand functionality, delete outdated tasks, adapt to evolving business logic, or replace old technologies. In the case of monolithic architecture, each of these changes leads to a complete overhaul of the entire system and its redeployment, incurring additional resource costs. Furthermore, during updates and modifications, the system may experience downtime or disruptions.

3. System performance: Since a monolithic system operates as a unified whole, all components share the same technical resources. If one component starts consuming a significantly higher amount of computational power, it can cause other parts of the system to fail due to insufficient shared resources.

4. Low fault tolerance: A failure in one part of the system can lead to cascading issues, impacting all interconnected components or even causing the entire system to fail.

5. Technological limitations: A monolithic system is built using a fixed set of technologies, making it harder to integrate with other tech stacks. Over time, this can limit the system's functionality and adaptability.

6. Support and development: Building and maintaining a large monolithic system requires big teams that must collaborate closely. This can lead to increased costs for team maintenance and ensuring efficient internal communication.

With these drawbacks, using monolithic architecture for designing information systems might not seem like the most reasonable choice. But don’t make conclusions just yet. Let’s take a closer look at the advantages and disadvantages of distributed architectures built on microservices.

Microservices Architecture

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The microservice architecture enables the implementation of any system as a collection of independently operating services, each of which is an autonomous element of the overall system and responsible for specific functionality. Communication between these services is facilitated through custom-developed APIs.

Key characteristics of such a system include:

• Service autonomy: Each service within the system operates independently. This eliminates the need for unified standards and technologies, allowing each service to implement the most effective business logic for its specific purpose.

• Separate databases for individual services: Each service can have its database if necessary, with data formats tailored precisely to its specific tasks.

• API interfaces: All services interact with one another through dedicated APIs, which optimize internal system communications and enable more efficient management of these interactions.

• Distributed deployment: Services within the system are not only autonomous in their operation but can also be developed and deployed independently of one another.

Let's look at the advantages of microservice architecture:

1. Scalability: This is the first and the most important advantage of microservice architecture. Each microservice can be modified independently of others, functionality can be extended for specific services, and new services can be added. This allows for efficient resource allocation and ensures optimal performance.

2. Rapid delivery and deployment: Since each service is developed independently of the entire system, development, testing, and deployment can occur autonomously, without affecting the system's overall functionality.

3. System flexibility: Each microservice operates autonomously, uses its database, and can leverage the most suitable technology for its specific processes. The system functions as a flexible set of services that can be modified and adapted to new requirements quickly without disrupting overall system performance. Additionally, development and support can be handled by different specialists working independently, enhancing flexibility in development and deployment.

4. Fault isolation: In case of a failure in one of the services, the system's functionality remains unaffected. The faulty service can be isolated and deleted without impacting the rest of the system.

However, despite all the advantages of microservice architecture that emerged through the evolution of monolithic architectures, microservices also come with their own set of drawbacks:

1. Complexity in management: Microservice architecture forms the foundation for a highly heterogeneous system. Each service is developed by a separate team, often using different technologies. These services operate independently, requiring the organization of a complex communication system. Managing and moderating such a system becomes a challenging task. Additionally, each service operates with different data formats and its database, which necessitates additional systems for reconciling and transferring data.

2. Increased overhead costs for system maintenance: To ensure smooth system operation, additional tools (e.g., APIs or message queues) are required, which demand extra resources for their implementation. This also leads to higher expenses for developers who need to create and maintain new communication channels.

3. Challenges in system debugging: The more complex a deployed distributed system of microservices becomes, the harder it is to ensure its uninterrupted operation and to coordinate interactions between multiple services. This complexity can make it problematic to resolve internal system errors, especially as scaling may disrupt the logic of business processes.

And despite the fact that the list of disadvantages for microservice architecture is shorter than that of monolithic architecture, these drawbacks can lead to significant challenges, with solutions that may become extremely costly.

Let’s create a visual summary of the differences between monolithic and microservice architectures:

Considering the characteristics of monolithic and microservice architectures, the following phased factors should be taken into account when choosing the architecture for your project:

• Project size and complexity,

• Scalability and flexibility requirements at the project start and for future growth,

• Available development team composition,

• Initial project budget,

• Desired time-to-market.

Based on these factors, it can be concluded that monolithic architecture will be a more suitable solution for:

1. Systems supporting small and medium-sized businesses,

2. Prototypes - testing hypotheses, rapid idea launch, and concept viability checks,

3. Limited technical resources with no plans for future expansion,

4. Systems that perform a small set of functions without the need for future scaling,

5. Systems with standardized initial requirements that won’t undergo significant changes in the future,

6. Applications that require high performance and minimal system response time,

7. Any system where the speed of production deployment is more important than internal structural flexibility.

Microservice architectures, on the other hand, will be more suitable for the following tasks:

1. Large and complex systems whose logic allows for the division of the architecture into several autonomous parts that can be designed, developed, and deployed independently of each other,

2. Systems that may experience variable or unpredictable workloads, where a distributed architecture ensures overall system stability and efficient use of computing resources,

3. Systems with a variety of business processes that require different technologies to ensure maximum efficiency,

4. Projects that involve continuous development, requiring continuous integration and deployment of new system modules,

5. Systems that will need constant technology updates,

6. Systems are expected to scale over time, adding new business processes and internal communication logic between system components,

7. Systems that are projected to require significant computing power, which is more effectively handled by a distributed microservice architecture.

And this, as you can imagine, is far from an exhaustive list of potential applications for both monolithic and microservice architectures. Each new system will share similarities with existing systems of its type, but it will also have its unique characteristics.

If your system has mixed requirements and attributes that present an approximately equal number of considerations for or against using monolithic or microservice architecture, consider the following options when designing:

• Creating a hybrid architecture, where different parts of the system implementing different business logic are built using both monolithic and microservice architectures. This approach can provide greater flexibility where needed and enhanced stability in other areas.

• Planning for architectural evolution as the system develops. For example, when building a monolithic system, design it with the possibility of integrating microservices through the creation of APIs.

Choosing the future architecture of your system is not just about addressing current challenges. It's a strategic long-term decision that will impact the system throughout its lifecycle. You need to evaluate not only your initial resources and goals but also the project’s global objectives, its potential for growth, and the trends within the domain for which the system is being created.