The mobile app architecture guide

When you hear the word architecture, what is it that immediately comes to mind?

Most likely, it’s your house. And that’s natural.

Architecture simply refers to the internal structure of something—be it an office building or your car.

Mobile apps have their own architecture, too.

In fact, architecture is one of the most important factors in development because it greatly impacts app efficiency, stability, and security.

This article will discuss some common types of app architecture and why they’re important in app development.

What is mobile app architecture?

In app development, architecture refers to an app’s rules, processes, and internal structure—essentially, how it’s built.

It determines how the different components communicate with each other to process app inputs and deliver output for the user.

Here’s an example of what mobile architecture looks like:

Mobile architecture

A good analogy for this is the human body. All your body parts are arranged in a way that allows you to move, breathe, and otherwise perform efficiently.

Any changes in the structure of your organs would affect the body irreversibly—even get it to shut down completely.

The same is true with mobile app architecture.

Now, you shouldn’t confuse app architecture with a tech stack—although they’re related.

Tech stack refers to the technologies and tools used to build an app, such as programming languages, third-party plug-ins, and hardware platforms.

Tech stack

On the other hand, architecture describes how these technologies are arranged inside the app.

Furthermore, it goes beyond the tools and into the other parts of the app, such as the data and the users.

Put another way, the tech stack is simply one aspect of mobile app architecture.

Why is the architecture of a mobile app important?

Simply put, properly designed architecture makes the mobile app much more stable, efficient, and easier to work with.

One of the main benefits of app architecture is modularity. It means your app is divided into components that can be developed, updated, and tested independently.

Martin Fowler, an esteemed software developer, highlighted the benefits of modularity clearly when he said:

A good architecture is important, otherwise it becomes slower and more expensive to add new capabilities in the future.

For example, suppose you want to introduce a new feature to your app.

When you’re dealing with modular architecture, it’s simple. Just code the new feature separately, then integrate it into the existing app.

Otherwise, you’ll need to modify the entire app, which is costly and time-consuming.

Modularised app architecture

Thanks to modularity, good architecture also allows for reusability. This allows you to use a single code in multiple projects, saving you tremendous development time and effort.

For instance, you can reuse a database management component on multiple apps that share the same database system.

Or, you can adapt a sorting algorithm from a previous project instead of creating it from scratch.

App architecture is also crucial for improving security. That’s because it allows you to compartmentalize sensitive data and code, then build security protocols around them.

For instance, you can put SSL encryption between the client machine and the code logic in the web server.

You could then boost your data security further by adding a layer of encryption around your database.

Data security using SSL Encryption

Ultimately, well-devised app architecture helps you deliver a safe and bug-free app while saving you time and money in the process.

Fundamental layers in mobile app architecture

Most types of app architecture are composed of three layers—the data layer, the business layer, and the presentation layer.

Here’s how they go together:

Fundamental layers in mobile app architecture

Let’s discuss each layer briefly.

Data layer

The data layer is the intermediary between the other app layers and external resources.

Its main purpose is gathering raw data from various sources (such as the database, cloud server, or an API) and then sending it to the upper layers, and vice versa.

For example, when a user requests the app to display their profile, the data layer connects to the database and asks for all the relevant data such as name, birthday, photo file, and others.

However, the data is still unprocessed at this point, so it might contain attributes like tags or IDs that the user shouldn’t see. The responsibility of cleaning this data falls to the business layer.

Since raw data is highly vulnerable and sensitive, the data layer should have ample security.

Proper data segregation from various sources is critical here, as mixing them is considered bad practice.

Business layer

The business layer contains the application’s core logic—the exact instructions on how it should behave.

It often takes user input or raw data from the data layer, processes it, then sends it to the presentation layer.

As an example, take a simple calculator app. When you use it to add two numbers, it’s the business layer that performs the actual computation.

The answer is then sent to the UI to be displayed.

The business layer is the most complex part of your app. It’s usually divided into multiple sublayers or components, each responsible for specific functionality.

For instance, if you have an enterprise resource management (ERP) app, the business layer might have components for warehouse and inventory management.

Business layer

Also, note that the business layer doesn’t necessarily have to be in the user’s app. Some or all of it can be contained in the server, with the app acting mostly as the UI.

Presentation layer

The presentation layer, or front end, is the visible part of the app—the part that the user actually sees. As you can guess, the app’s user interface (UI) is a big part of this layer.

The main purpose of the presentation layer is to take the data sent by the business layer and display it in a way the user understands.

A simple example is the UI displaying a user’s email address, which is extracted by the data layer from a database.

However, the presentation layer can also use the data and display it in complex ways.

A good example is a stock trading app. It takes live data about the stock exchange (from an external website via an API) and displays it as a graph or chart.

Stock trading app UI

While developers are mostly responsible for the business and data layers, the presentation layer is the domain of the UI and UX designer.

Their goal is to make the UI screens as user-friendly as possible.

Types of mobile app architecture

This section will discuss the three common types of mobile app architecture, including their pros, cons, and use cases.

Layered architecture

Layered or N-tier architecture is where components with similar logic or purpose are grouped, then organized into several layers or tiers.

This is the type of architecture typically used for on-premise software.

N-tier applications usually include the three layers we discussed before—data, business (or application), and presentation.

However, some apps can rely on four or five-layer architecture, depending on the circumstances.

Here’s an example of a five-tier app:

Five layer architecture

Layers can only interact or pass data to and from an adjacent layer. This is one of the key principles of this type of architecture, as it helps manage dependencies and enforce security.

For example, the client layer can’t directly access the data layer because that would be risky.

Instead, it has to pass through the business and integration layers, which contain the necessary safeguards and security checks.

N-layered architecture is generally easy to understand and manage—but only to a point. With larger apps, it gets harder to pinpoint which layer an error comes from.

Often, this involves troubleshooting multiple layers.

Monolithic architecture

In the monolithic type of architecture, all the app components are tightly integrated, and function as a single unit called a monolith. It’s an approach that you’ll often see in older systems.

Monolithic architecture

The biggest reason to use monolithic architecture is simplicity. Since a monolith has fewer moving parts, it’s easier for developers to create, test, and deploy it as a self-contained app.

As such, monoliths are best for smaller, less complex apps or if you’re a start-up on a tight budget.

Otherwise, monolithic apps aren’t recommended because they’re extremely limiting.

If you want to change a feature or introduce a new one, you’d need to modify the entire codebase because everything is interconnected.

This makes updating and scaling them exceptionally costly and time-consuming.

You’re better off either with a layered or a microservices approach.

Microservices architecture

The microservices type of architecture divides the app into smaller components called a microservice.

Each microservice is completely standalone and can function without needing any other component.

The main client app then uses an application programming interface (API) to communicate with them, as shown below:

Microservices architecture

Microservices architecture represents the most flexible and fluid approach to developing software.

That’s because each app functionality can be developed, tested, and deployed independently.

Adding or editing new features is trivial—you just need to modify the relevant microservice, then have the client app call it via the API.

Microservices enable development teams to scale, fix, and upgrade apps rapidly.

However, the big drawback is that microservices architecture can be tricky to deploy since you must do it multiple times for each microservice. This gets trickier the larger the application.

Nevertheless, microservices are the best approach for developing complex cloud and hybrid applications.

Types of mobile app architecture patterns

Another way to define app architecture is through the pattern model. Let’s discuss the three common types to give you a better idea.

Model-View-Controller

The Model-View-Controller (MVC) is the simplest architecture pattern.

Here’s how it looks:

MVC

The Model component is responsible for data handling, similar to the data layer. It contains the code for getting data from sources like a database, a microservice via an API, or a JSON object.

The Controller component processes the data from the model component and sends it to the view component, essentially acting as the link between them.

This is where your app’s core logic and algorithms are contained.

The View component is responsible for what the user sees—or the UI.

The MVC architecture is the default for iOS apps, which explains its popularity. Its simplicity is one of its advantages.

However, here at DECODE, we realized over time that MVC could become tedious and unwieldy for large, complex apps.

Model-View-Presenter

The Model-View-Presenter (MVP) architecture is another common pattern used extensively in Android development.

It looks like this:

MVP

The MVP architecture has many similarities with MVC. Here, the Model component also handles the data, and the View component is for the UI.

The Presenter component is analogous to the Controller component in the MVC model, containing the logic that processes data for the user.

However, a big difference is that in the MVP model, the View component is in charge.

That means it initiates requests to the Presenter and Model. In the MVC architecture, the Controller is in charge.

Thus, Views are reusable in the MVP model, which makes it more modular and reusable than an MVC application.

Model-View-ViewModel

The Model-View-ViewModel (MVVM) architecture separates the code logic as follows:

MVVM

View, as always, houses the visual elements like UI and text. However, unlike the MVC and MVP models, the View component can’t change the UI elements directly.

Instead, the MVVM uses data binding for this purpose. It acts as the bridge between the View and ViewModel components.

The ViewModel contains the application logic, while the Model handles the data.

What this means is that the ViewModel can effectively work without having to know the View component.

This leads to a higher separation of logic, making an MVVM app easier to maintain than MVP and MVC, which is why we use it at DECODE.

So, which type of architecture should you choose?

We hope you’ve gained a sense of understanding and appreciation for different types of mobile app architecture.

Of course, this begs the practical question—which type of architecture is right for your app?

Unfortunately, there’s no general answer to that. It will depend on the circumstances of your project.

Instead, why not give us a call?

Schedule a FREE consultation (fully backed by an NDA), and let’s figure out the best approach for your project!