Choosing the right architecture for a software project is a momentous decision. After all, it constitutes the skeleton that will support all subsequent development, its maintenance, scalability, and security. In addition, it will be fundamental for the platform's operation and the users' experience.
In the field of software architectures, the monolithic and microservices-based models are two of the most common options. Both have specific characteristics, strengths, and weaknesses that each organization must carefully consider before deciding. Below, we analyze them in detail.
Monolithic architecture
A monolithic architecture refers to an application built as a single, cohesive unit. All its components (user interface, business logic, data access, etc.) are interconnected and run as a single process.
The fundamental design principle of a monolith is its high coupling. All parts of the application are so interconnected that a change in one section of the code can impact other areas of the system.
This interconnection simplifies the initial development but generates an increasing maintenance burden as the system scales, masking latent complexity in the medium and long term.
Strengths
Although monolithic architecture may be somewhat outdated for some companies, it remains a very popular approach due to its initial simplicity, lower technical complexity, and economic accessibility.
Simplicity in initial deployment
One of the main strengths of monoliths is their ease of development and initial deployment. This is because all functionalities reside in a single codebase, which streamlines coordination among different functions and development processes.
The project deployment is simple since everything is managed in a single executable file or a very small set of files, eliminating the need to configure multiple runtime environments.
Lower technical complexity
In general, monoliths do not require complex infrastructure or the management of distributed processes. For this reason, the initial implementation costs are significantly lower.
This is a fundamental feature for emerging teams and projects, as they have the opportunity to experiment and create products without heavy financial investments in the early stages.
Fast MVP validation
The simplicity of monoliths makes them a catalyst for rapid prototyping and validation of markets, concepts, or business models. For development teams with limited resources, monoliths are the most suitable option in the validation stage, enabling more agile progress.
As prototypes go through different iteration cycles, developers can gradually explore the system's complexity and adjust the approach based on feedback.
Challenges
Nowadays, applications or platforms developed as monoliths face several critical difficulties for their future evolution and sustainability. Let’s look at some of the most important ones.
Scalability limitations
Since all components share a single environment, it is difficult to scale specific parts of the application independently.
Monoliths rely mainly on vertical scaling, which involves increasing the capacity of a single server (adding more RAM or CPU). This strategy has physical limits and can become costly quickly.
Increasing maintenance difficulties
As a monolith grows, the time required to implement new features increases significantly. Modifications in one part of the system often affect other areas due to the strong coupling, which can lead to unexpected failures in other functionalities.
No matter how small a change is, the modification will require recompiling and deploying the entire application. This process greatly increases the risk of cascading errors and exposes the application or product to downtime that negatively impacts customer experience and business agility.
Lack of technological flexibility
Since everything is built with the same technology, flexibility to adopt new tools or languages in specific components is more limited.
In this scenario, the software can easily become obsolete compared to competitors who can update more easily.
Furthermore, if the application needs to be updated, the entire system will have to be refactored, which involves a considerable investment of time and money.
Microservices architecture
In addition to the monolithic approach, numerous organizations and companies have opted for microservices-based architecture. In this scheme, applications are built as collections of small, autonomous, loosely coupled services, where each microservice is designed to fulfill a specific business function and manage independent tasks.
Essentially, microservices architecture decomposes a large, complex application into smaller, independent, and manageable units. Each unit communicates with others through well-defined interfaces, such as REST APIs or message queues.
The microservices approach is a very interesting software alternative for companies betting on a more modern development approach with better future projection, even when the initial investment and technical complexity are high.
Strengths
Microservices represent a development approach driven by greater scalability, fault tolerance, and technological flexibility. These and other traits make this style an attractive option for cutting-edge technology companies.
High horizontal and granular scalability
This is one of the strongest points of software architecture based on microservices. Each module can scale independently according to its own demand.
This means that only the parts of the application experiencing excessive load can be scaled without the need to scale the entire system. For example, if payment processing has a usage peak, that will be the component scaled, not the whole integrated system.
Individually scaling each component results in a more efficient use of available resources and, even more importantly, the ability to introduce new components or increase capacity without disabling the rest of the platform.
Greater resilience and fault tolerance
Since each unit works independently, if an error occurs in one service, it will not spread throughout the system, preventing cascading failures and ensuring that the rest of the platform works and is available to users, even when a component is being reviewed.
This is possible because microservices architecture applies the principle of design for failure, a proactive system engineering approach that involves planning and building environments with the expectation that failures will occur. Thus, the system can be designed to effectively handle errors when they arise.
Greater technological flexibility
Microservices allow choosing the best programming language, framework, and technology stack for each individual service based on its unique requirements.
This flexibility avoids vendor lock-in and enables the use of the best tools for each task, optimizing performance, development efficiency, and platform management.
Challenges
Although more advanced than monoliths in several aspects, the microservices approach brings with it some difficulties regarding investment, specialization, management, and more.
Infrastructure and team cost
Setting up a microservices architecture is more expensive than a monolith, as it involves managing numerous services that must communicate with each other. This generates higher initial development investments, since a more complex distributed infrastructure is required and costly to configure.
This also leads to a heavy human talent expense, as managing the infrastructure will require organizing multiple teams, each dedicated to a specific component. Moreover, talent costs increase because professionals with more specialized skills are needed.
Distributed data management
Deciding that each microservice should have its own database promotes independence but also presents major challenges in data management.
On one hand, ensuring data consistency across multiple distributed stores is a complex problem, especially for transactions. Often, this requires implementing advanced strategies such as the Saga pattern or event-driven architecture, all to maintain information coherence.
Greater organizational overhead
Compared to a monolithic architecture, organizational overhead is significantly higher in a microservices scheme due to the need for coordination and communication between multiple autonomous teams, each working on a specific component of the platform.
There is also a greater effort to standardize the tools that will be used in the different components. Although each team has freedom to choose technologies, a minimum level of governance must exist so that diversity does not become excessively difficult to manage.
Monoliths and microservices face to face
Costs
Initially, a monolith is cheaper to build, as it requires less infrastructure, tools, and specialized expertise. However, as the application grows and becomes more complex, maintenance and scalability costs can skyrocket.
On the other hand, microservices demand a much higher initial investment in infrastructure and teams. Nonetheless, in the long run, maintenance costs are significantly lower due to their modularity and scalability.
Scalability
Monoliths scale vertically. To handle more load, it is necessary to increase the resources of the server where the entire application resides. If only part of the platform is under pressure, upgrading the entire server is inefficient.
In contrast, microservices allow horizontal and selective scaling. Only the service experiencing high demand will be scaled, optimizing resource usage and costs. More importantly, the process of scaling a single component of the platform allows it to continue operating normally.
Maintenance
Maintaining a monolith is more straightforward in the initial stage, as there is only one codebase to manage and a single deployment process. However, maintenance becomes more complex as the platform grows, and changes in one sector may unexpectedly affect others.
In microservices, maintenance is distributed by components. While this facilitates individual monitoring of each microservice, managing the system as a whole is more complex due to the multiplicity of logs. This requires a robust DevOps culture that may not be available or sufficiently developed in all organizations.
Complexity
Monoliths are less complex in the early stages compared to microservices. Managing the entire platform in a single codebase makes them a better option for creating prototypes that allow validating work hypotheses and accelerating time-to-market.
In contrast, complexity is inherent to microservices. From initial design to deployment and operation, they introduce significant challenges in:
- Communication between services.
- Communication between work teams.
- Distributed data consistency.
- Failure handling in a distributed environment.
Return on Investment
The project context is the main determinant of the ROI of each architecture.
In small projects, startups, or proof of concepts, the monolith offers a faster return on investment (ROI) due to its lower initial cost and faster development speed. It allows validating ideas quickly without significant investment.
In large-scale initiatives, the initial investment in microservices, though high, can generate a higher return on investment in the long run. This will be possible thanks to scalability efficiency, reduced maintenance costs, and the ability to deploy new features more agilely.
