When starting a new development project — whether for a new product or an internal business solution — several decisions must be made: choosing the programming language, defining infrastructure, modeling the database, and more.

Beyond these technical foundations, it’s also essential to decide how to organize code modules and components. Traditionally considered “non-functional requirements,” factors like scalability, failure resilience, low coupling, and ease of maintenance and continuous delivery are now central architectural concerns.

With the rise of microservices, many teams have moved away from traditional monolithic approaches and adopted microservices from day one. But it’s worth asking: Are we adding unnecessary complexity to an already volatile development process? Do microservices really deliver the competitive edge we expect?

Faced with these doubts, this article presents some practical criteria to help you evaluate which architecture is best for your project — before the complexity grows to the point of compromising the agility and value delivered to the business.

First of All, Let’s Contextualize

Before exploring the decision criteria, let’s quickly define the two dominant architectural styles to set a shared foundation.

What Is Microservices Architecture?

Microservices architecture breaks a system into small, independent services, each with well-defined responsibilities.

Each service can be developed, deployed, and scaled independently, supporting flexibility, resilience, maintainability, and continuous delivery.

What About Monolithic Architecture?

In a monolith, the system is built as a single, integrated application. All components share the same codebase and usually the same database.

Though simpler to implement initially, monoliths can become unwieldy as the system grows — especially regarding scalability, maintainability, and deployment agility.

Starting the Discussion

As these definitions show, microservices offer theoretical advantages. However, we know that practice does not always follow theory.

Real-world factors — both technical and business-related — usually have much greater weight in the decision than any academic definition.

Technical Considerations

Let’s start by analyzing the technical criteria, which are part of the daily life of development teams and help guide the best choice of architecture.

System Complexity

If your application is small or just getting started, a monolith may be more practical. However, consider this:

If your system spans multiple business domains — where Domain-Driven Design (DDD) can help identify boundaries — or has strong potential for future growth and complexity, starting with microservices can be strategic.

Scalability

Monoliths, in general, have limitations when it comes to scalability. They typically scale vertically — by adding memory or CPU to the host machine. If this meets your needs, there may be no reason to change.

On the other hand, if there is a requirement for horizontal scalability — such as service replication, load balancing, and elasticity — distributed architectures like microservices become the best option from the start.

Team and Culture

This point is often neglected. If your team lacks experience with distributed systems or DevOps practices like CI/CD and monitoring, starting with microservices may create more headaches than benefits.

In these cases, a well-structured monolith can offer much more predictability and facilitate the gradual evolution of the team.

Deployment Frequency

Ask yourself:

• How many deployments do you expect per day or per month?
• What is the release frequency?
• How automated is your testing and delivery process?

If your team already follows mature continuous delivery practices, microservices may boost agility. Otherwise, opting for a more centralized and controlled approach can avoid many problems and rework.

Maintenance and Evolution

It is common for monoliths to become more difficult to maintain over time. However, this is not a rule: there are well-designed monoliths where maintenance is fluid. Still, there is always the risk that an error in one part of the code will affect the entire system.

In microservices, this is one of the great advantages: the code is modularized, and each service has its own repository, versioning, and delivery pipeline. This facilitates maintenance and continuous evolution. However, be careful: the organization must be rigorous, as fragmentation also brings challenges.

Resilience and Independence

Monoliths are susceptible to cascading failures. A problem in one module can compromise the entire application, impacting users and operations.

In a microservices architecture, failures tend to be isolated, allowing parts of the system to continue functioning normally. However, this requires each service to have its own set of monitoring, tracking, and observability practices. Ideally, the team should identify problems before the user.

Development Time and Initial Cost

Evaluate:

• What is the available budget?
• What is the deadline for the first delivery?
• Do you have specialists in infrastructure, orchestration, and automation?

Microservices require a greater investment in time, team, and structure. For small projects or MVPs, the monolith is usually more agile and economical.

On the other hand, for long-term solutions, with multiple teams working simultaneously and with available investment, microservices offer scalability, flexibility, and robustness from the foundation.

Business Considerations

After evaluating the technical criteria, it’s equally important to weigh business goals. After all, it is usually the business team that directs investments and defines the expected value of the solution. Therefore, their needs and expectations must also be considered when choosing the ideal architecture.

Time-to-Market

More robust and complex architectures, such as microservices, can increase the time needed to launch a product on the market. This can cause the company to miss the ideal timing and, consequently, valuable opportunities.

In this case, it is worth reflecting: Is your team prepared to live with this initial impact, or would it be more appropriate to opt for a simpler solution with a leaner infrastructure that allows for faster delivery? This is a key criterion in decision-making.

Initial vs. Long-Term Cost

From a financial point of view, a monolithic system has a much lower initial cost, especially regarding infrastructure. However, over time, limited scalability (usually vertical) can significantly increase operating costs.

A microservices architecture may require a higher initial investment due to the need for a distributed infrastructure, orchestration, and observability mechanisms. However, over time, these costs tend to stabilize or even decrease, thanks to the possibility of more precise adjustments in autoscaling, resource allocation, and architectural refinement based on real usage data.

Growth Expectations

If your product is expected to grow rapidly, the architecture must keep pace. Monoliths can become bottlenecks if not structured well, making it difficult to add new features and limiting evolution.

By their modular and independent nature, Microservices offer greater agility to scale specific parts of the system, facilitating continuous growth and the maintenance of multiple versions of the solution in parallel.

Product Flexibility

Scope changes are inevitable — new ideas, market opportunities, and user feedback require flexibility. In this scenario, microservices tend to offer greater malleability, allowing you to test hypotheses and adjust features with less impact on the system as a whole.

However, this advantage depends directly on the level of coupling between services, the organization of the code, and the technical maturity of the team.

Compliance and Security

When the focus is on regulatory compliance and security, monolithic systems usually have an advantage. Dependency updates, patches, and certifications are centralized, streamlining compliance.

In microservices, these updates need to be replicated in multiple pipelines and instances, which increases the time and effort to ensure compliance and security across the solution. Therefore, it is important to consider the maintenance cost and the additional complexity in this aspect.

The Verdict

There’s no one-size-fits-all answer — each project has its own reality, its challenges, and its priorities.

We have long ceased to believe in the “silver bullet” — that universal and definitive solution. Instead, when it comes to software architecture, what we really have are criteria that must be carefully analyzed to guide the best decision according to the technical and business context.

In the end, the choice of architecture must be aligned with what generates the most value for the business and more efficiency for the delivery of the solution. The points addressed above serve as a guide so that you and your team can make decisions more clearly, reducing uncertainties and increasing confidence in the path to follow — whether building new projects or evolving existing systems.