What’s the Difference Between Monolithic and Microservices Architecture?

Monolithic applications typically consist of a client-side UI, a database, and a server-side application. Developers build all of these modules on a single code base.

On the other hand, in a distributed architecture, each microservice works to accomplish a single feature or business logic. Instead of exchanging data within the same code base, microservices communicate with an API.

Next, we discuss more differences between the two.

Read about APIs »

Development process

Monolithic applications are easier to start with, as not much up-front planning is required. You can get started and keep adding code modules as needed. However, the application can become complex and challenging to update or change over time.

A microservice architecture requires more planning and design before starting. Developers must identify different functions that can work independently and plan consistent APIs. However, the initial coordination makes code maintenance much more efficient. You can make changes and find bugs faster. Code reusability also increases over time.

Deployment

Deploying monolithic applications is more straightforward than deploying microservices. Developers install the entire application code base and dependencies in a single environment. 

In contrast, deploying microservice-based applications is more complex, as each microservice is an independently deployable software package. Developers usually containerize microservices before deploying them. Containers package the code and related dependencies of the microservice for platform independence.

Read about containerization »

Debugging

Debugging is a software process to identify coding errors that cause the application to behave erratically. When debugging monolith architecture, the developer can trace data movement or examine code behavior within the same programming environment. Meanwhile, identifying coding issues in a microservice architecture requires looking at multiple loosely coupled individual services. 

It can be more challenging to debug microservice applications because several developers might be responsible for many microservices. For instance, debugging may require coordinated tests, discussions, and feedback amongst team members, which takes more time and resources. 

Modifications

A small change in one part of a monolithic application affects multiple software functions because of the tightly coupled coding. In addition, when developers introduce new changes to a monolithic application, they must retest and redeploy the entire system on the server.

In contrast, the microservices approach allows flexibility. It’s easier to make changes to the application. Instead of modifying all the services, developers only change specific functions. They can also deploy particular services independently. Such an approach is helpful in the continuous deployment workflow where developers make frequent small changes without affecting the system's stability. 

Scaling

Monolithic applications face several challenges as they scale. The monolithic architecture contains all functionalities within a single code base, so the entire application must be scaled as requirements change. For example, if the application's performance degrades because the communication function experiences a traffic surge, you must increase the compute resources to accommodate the entire monolithic application. This results in resource wastage because not all parts of the application are at peak capacity.

Meanwhile, the microservices architecture supports distributed systems. Each software component receives its own computing resources in a distributed system. These resources can be scaled independently based on current capacities and predicted demands. So, for example, you can allocate more resources to a geographic location service instead of the whole system.

Both monolithic and microservices architecture help developers to build applications with different approaches. It's important to understand that microservices don't reduce the complexity of an application. Instead, the microservices structure reveals underlying complexities and allows developers to build, manage, and scale large applications more efficiently.

When you decide between developing a microservices or monolithic architecture, you can consider the following factors.

Application size

The monolithic approach is more suitable when designing a simple application or prototype. Because monolithic applications use a single code base and framework, developers can build the software without integrating multiple services. Microservice applications may require substantial time and design effort, which doesn't justify the cost and benefit of very small projects. 

Meanwhile, microservices architecture is better for building a complex system. It provides a robust programming foundation for your team and supports their ability to add more features flexibly. For example, Netflix uses AWS Lambda to scale its streaming infrastructure and save development time.

Read how Netflix uses Lambda »

Team competency

Despite its flexibility, developing with microservices requires a different knowledge set and design thinking. Unlike monolithic applications, microservices development needs an understanding of cloud architecture, APIs, containerization, and other expertise specific to modern cloud applications. Furthermore, troubleshooting microservices may be challenging for developers new to the distributed architecture. 

Infrastructure

A monolithic application runs on a single server, but microservices applications benefit more from the cloud environment. While it's possible to run microservices from a single server, developers typically host microservices with cloud service providers to help ensure scalability, fault tolerance, and high availability.

You need the right infrastructure in place before you can start with microservices. You require more effort to set up the tools and workflow for microservices, but they are preferable for building a complex and scalable application.

Category	Monolithic architecture	Microservices architecture
Design	Single code base with multiple interdependent functions.	Independent software components with autonomous functionality that communicate with each other using APIs.
Development	Requires less planning at the start, but gets increasingly complex to understand and maintain.	Requires more planning and infrastructure at the start, but gets easier to manage and maintain over time.
Deployment	Entire application deployed as a single entity.	Every microservice is an independent software entity that requires individual containerized deployment.
Debugging	Trace the code path in the same environment.	Requires advanced debugging tools to trace the data exchange between multiple microservices.
Modification	Small changes introduce greater risks as they impact the entire code base.	You can modify individual microservices without impacting the entire application.
Scale	You have to scale the entire application, even if only certain functional areas experience an increase in demand.	You can scale individual microservices as required, which saves overall scaling costs.
Investment	Low upfront investment at the cost of increased ongoing and maintenance efforts.	Additional time and cost investment to set up the required infrastructure and build team competency. However, long-term cost savings, maintenance, and adaptability.