The disadvantages of Monolithic Application Architecture you should know

Monolithic architecture is the classic way of software development wherein all components are built as a single code and deployed as a single file. However, a new kind of architecture, microservices, has been gaining popularity among businesses. Essentially, businesses today have two broad choices to roll out technology stacks—either deploy a single platform that combines many functions or use microsystems to integrate discrete services from different vendors. This article explains the basics, pros, and cons of these two approaches and the key disadvantages of monolithic application architecture you should know.

• What is Monolithic Architecture?
• Types of Monolithic Architecture
• Microservices Architecture
• How does Monolithic Architecture compare to Microservices?
• When to use a Monolithic Architecture?
• Tips to Migrate from a Monolithic Architecture to a Microservices Architecture

What is Monolithic Architecture?

Monolithic Architecture is the traditional, all-in-one structure for software applications wherein all aspects of software operate as a single unit. More often than not, a piece of software is a combination of different feature sets. In monolithic architecture, all software features exist in a single code base and are deployed as a single file. If any code updates are required, the developer has to use the same code base, make the required changes, and re-deploy the updated code. In a related article, we discussed scalable web application architectures that can host millions of users. Monolithic software applications can have the following components:

1. Authorization: responsible for authorizing a user.
2. Presentation: handling HTTP requests and responding with HTML or XML/JSON
3. Business logic
4. Database layer: data access objects responsible for accessing the database
5. Application integration: integration with other services or other data sources.
6. Notification module: sending email/pop-up notifications whenever required.

An e-commerce application is a good example of a monolithic approach. A single app authorizes the customer, takes an order, checks inventory, authorizes payment, and ships ordered products. Despite having different components/services, the app is built and deployed as one application for all platforms (i.e., mobile, tablet, desktop).

Types of Monolithic Architecture

There are mainly two types of monolithic architecture:

1. Single Process Monolithic Architecture: when all the code of an application is deployed as a single process.
2. Modular Monolithic Architecture: where a single application process consists of multiple modules, each of which can work independently. The modules can communicate with each other through interfaces. All the modules work on the same underlying database but are still independent and must be combined to form a single file for deployment.

Monolithic architecture is often compared to microservices architecture because of the latter’s many benefits for business-oriented APIs. Let’s understand what microservices architecture is.

Microservices Architecture

A microservices architecture is an organizational approach to software development wherein software is composed of small, independent services that communicate through well-defined APIs. It is a distinctive method of developing software systems focussing on building single-function modules with well-defined interfaces and operations.

 Microservices are built as independent services wherein each service is a separate codebase manageable by a small development team. These services can be deployed independently, and a team can update an existing service without rebuilding and re-deploying the entire application, as in monolithic architecture. Typical microservices architecture usually has the following components:

1. Management: responsible for placing services on nodes, identifying failures, rebalancing services across nodes, etc.
2. API Gateway: the entry point for clients, which forwards their call to the appropriate services on the back end.

How does Monolithic Architecture compare to Microservices?

Microservices differ from monolithic architecture because they function as a loose collection of functionalities working together under a single application. Each service under an application may have its own database with a dedicated team working on it. While monolithic apps connect to a single database, each service in the microservices structure connects to its own database.

The two structures can be better understood with a practical example. A monolithic app may be a simple office suite software program in which an individual can download the entire application simultaneously. An example of a microservices app may be an online streaming platform with one microservice for onboarding new users, another for maintaining platform content, and another for recalling user preferences.

In fact, Netflix was one of the first online streaming platforms to use the microservices architecture. The platform struggled to keep up with the rapidly increasing demands of video streaming services. Hence, it migrated its IT infrastructure from private data centers to a public cloud. Though the term ‘microservices’ didn’t exist then, the platform won the 2015 JAX Special Jury award for its new infrastructure.

In light of these definitions, monolithic apps may seem simple and easier to handle. However, that is not always the case. We’ll now discuss some drawbacks of the same.

Disadvantages of monolithic application architecture

 The disadvantages of monolithic apps primarily arrive from their all-in-one structure.

1. Scaling: Monolithic apps operate on a single base of code, meaning any change, such as scaling, needs to involve the entire architecture. It is impossible to scale only one segment in monolithic apps This also contributes to slow development speed since the app is too large and complex to implement changes quickly. Moreover, scaling challenges may also arise when different modules have conflicting resource requirements.
   
2. Integration with new technology is challenging since the whole architecture needs to undergo a code rewrite. Monolith architecture also lacks flexibility by being constrained by the tech already used within the structure.
   
3. Monolithic apps are harder to rely on since an error in any of the modules can affect the entire application’s availability.
   
4. The large size of the application may slow down the start-up time.
   
5. Adopting new and advanced technologies isn’t cost-effective since a thorough effort is needed to work with all application modules.
   
6. Monolithic apps also make it difficult for organizations to integrate data from their systems. Typically, you can only use your data within the monolith app.

But does this mean that monolithic applications have no benefits at all? Not necessarily. Here are some ways in which monolithic apps prove to be beneficial.

When is a Monolithic App Beneficial?

1. Monolithic apps are easy to deploy. Monolithic architecture requires only a single file/directory to be launched.
   
2. Developing an application is easier when it is built with one code base.
   
3. Because a monolithic app is a single, centralized unit, performing end-to-end testing is faster.
   
4. Since all the code is located in one place, it is easier to follow to request and find an issue. For the same reason, there are also fewer security concerns. A single codebase simplifies logging, application performance monitoring, configuration management, etc.
   
5. Monolithic applications can easily be scaled by running multiple copies behind a load balancer.

The difference in software development for monolithic and microservices architecture

Traditional monolithic architecture often results in large teams working on a single artifact. They tend to evolve into a situation where no single developer can truly understand the entirety of the application. Moreover, the repeated deployment of monolithic artifacts makes it difficult to achieve operational agility.

A microservices architecture provides a different approach to software development. Essentially, the monolith is disassembled into a set of independent services developed, deployed, and maintained separately. This has various advantages, such as:

1. Services are encouraged to be small and are ideally built by a small team of developers.
2. Other applications and/or services can help consumers reuse services within a microservices structure through shared libraries and language bindings.
3. Services exist as independent artifacts and can be scaled independently.

When to use a Monolithic Architecture?

Despite the disadvantages of a monolithic application, there are some business use cases where monolithic architecture is the right choice.

1. Monolithic architecture can meet the requirements of start-ups and small teams that don’t have the resources required to implement a complex architecture.
   
2. It’s good to use monolithic architecture when developing a business proof of concept with fewer complexities.
   
3. Monolithic architectures are perfect for simple, small applications that do not contain much business logic and don’t need scalability and modularity.

Tips to Migrate from a Monolithic Architecture to a Microservices Architecture

Most projects initially start as a monolith and then evolve into a microservices architecture. This may be because too many developers work on a single codebase, leading to frequent code conflicts, or because of the increasing risk of updates to one feature introducing bugs in another. Here are a few tips businesses can keep in mind during their migration process.

1. Mapping out a migration strategy: planning the different dynamics and usage of the app beforehand.
   
2. Tooling: Investing in the right tools to make migration easier for the users. This could include tools that check codes for quality, privacy, service design, security, and reliability before production.
   
3. Embracing a culture shift: A migration is technical and affects the people and the organization. To ensure that your app continues working smoothly, embracing and accepting the operational changes that come with migrating to a different architecture is imperative.
   
4. Balance speed and trust: establishing a system of checks and balances that allows you to maintain high reliability with the users.

Closing Thoughts

In this article, we covered the disadvantages of a monolithic application. Both monolithic and microservices approaches to software development have their pros and cons. A monolithic architecture is best suited for simple, lightweight applications. However, as the app grows, traditional architecture is bound to face problems and demand more time and effort. More often than not, a shift to microservices architecture will be required. That said, it is important to understand the monolith architecture since that is the basis for microservices architecture.