The Guide to Web Application Architecture

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Modern application software gets increasingly complicated and multifunctional by the day. Most solutions we see and use nowadays are based on the complex structure consisting of the software code that interconnects a number of separate functional components: UI optimized for in-browser performance; calculating capacities; databases, etc. A total number of these components can vary dramatically. But what exact principles govern this initial separation by functional elements as well as the way they are interconnected eventually? It all depends on certain web application architectures. We will discuss the four major, most commonly used types and find out in which cases they are best implemented.

web app architecture

4 typical architectural patterns for web apps and their unique features

There are over a dozen models for building web apps out there. Nevertheless, the following four types of web application architecture models are the most commonly used ones so we’d like to shed some light on them.

A ‘client-server’ pattern (two-level pattern)

As you can see from the title, this pattern has two levels – there are visually-accessible components that let users implement certain actions within an app, and there are components that are hidden from regular users’ eyes, which are responsible for data reading and writing, connection with the server, and business logic operations. In detail:

  • Client – the architectural level of a web app that provides the visual representation of an app’s functionality for users. It is a launchpad mechanism for the initiation of further app’s operations, as it is the client who sets everything off at first – the server simply responds, letting one know whether it can provide a certain feature (process request) and in which way it can do that. From the technical point of view, such a connection is made possible via specialized network protocols, like IP, HTTP, HTTPS, FTP, and others. Client-side software and server-side software is usually based on different hardware, but they can work on one device in sync. Developers use HTML, JavaScript, and CSS, all of which aren’t limited in terms of OS compatibility (as opposed to desktop and mobile apps, only a browser is required here) to create the client side of the whole deal. Sometimes, software providers create special graphic consoles to manage the client side of an app, which grant several levels of access;
  • Server – the backend of an app where the whole business logic comes into motion. Here, programming languages of an imperative coding style come into play, such as Python and Java. This part of an app is managed by the software provider and, usually, a regular user doesn’t get to customize these basic settings.

Below, you can see a web application architecture diagram that demonstrates visually how the client-server pattern components work:

two level pattern

This type of architecture is quite costly, though. That’s why developers find a way to direct client requests in such a way that they go through a bunch of ‘layers’ – servers with different performance volumes – to reduce the load for involved systems. This is where the Layered pattern is usually implemented.

Layered pattern

This pattern has a bit more in-depth basic design as opposed to the previous option. The goal of structure separation here is to save the speed of performance upon high server-side loads. The load can depend on various factors – a large number of simultaneous users or the complexity of business logic that affects databases and client-side operations by serving as a base of all calculations within an app. Everything is getting balanced up with a subsequent request processing:

  • on the client level (presentation layer) – works just like in the previous pattern’s client part;
  • on the service level (business layer) – all the operations outside of the application area and its database;
  • on the business logic level (persistence layer) – all the involved calculating operations;
  • on the database level (database layer) – the database server that stores all the data an app operates with.

The layered type allows to evenly distribute the load to be processed by the calculating powers. On the other hand, incorrectly designed layers (or the presence of excessive layers) can negatively affect the quality of programmers’ performance, which may increase the risks of errors’ appearance and slow all the operations down.

And here’s a respective web application architecture diagram of the pattern for your visualization of the whole process:

layered pattern

Model-View-Control pattern

This here model serves as a foundation for most modern high-performance, scalable apps which involve several teams of experts to be implemented (these are, usually, enterprise-scale web apps). An MVC pattern subdivides interactive applications into three interconnected components:

  • Model – implies the direct management of data, logic, and rules lying in the core of an app. With any solution, the whole structure is modeled as data to be processed in a certain way. In such a way, the ‘model’ component provides a controller (another MVC pattern component) with the data representation requested by the user. The model of data will remain the same independently of how we intend to deliver it to a user. That’s why any available way to efficiently display the data is selected. The model contains the most important part of a web app’s logic – that which solves the task at hand. The controller, in turn, contains prevalently the organizational logic of an app (i.e., it describes HOW specific tasks must be solved);
  • View is a component that provides various ways to interpret the data extracted from the model. It works as a template filled up with data and so it usually represents itself in several different varieties for the controller to choose the most fitting format for a certain situation;
  • Controller – manages user requests (received in the form of HTTP GET or POST requests when a user clicks the interface elements to implement different actions). Its major function is to summon and coordinate the performance of resources and objects required to perform user-requested actions. The controller, usually, summons up the respective model for a certain task and selects the fitting view.

This pattern can be preferred by a software architect to isolate the data from any customizations in how they are presented to users and how they return from users. It comes in very handy when several departments are working on a single app. On the other hand, an MVC model increases the overall project complexity. Here’s a web app architecture diagram for this pattern:

model view

Notice that during recent years, as web solutions become increasingly more complicated, there have appeared a number of modern web application architecture alternatives to the MVC: HMVC, MVVM, and others.

Read also: How to Develop a PWA

Peer-to-peer pattern

Under this pattern, an app is separated into several equal-rights components, each of which can serve both as a client and a server. It implies fully decentralized structures. In all the rest, interaction principles and component roles are identical to the first discussed pattern – ‘client-server’.

Here’s how a P2P pattern implementation looks like:

peer to peer architecture

The most frequent cases of settling with this web system architecture model are web apps that require the distribution of powers among multiple servers (to achieve maximum accessibility and failure safety). This is also a good sufficient model for applications with further scaling prospects. As for some downsides of the P2P architecture pattern – the overall performance depends on the number of nodes and support for individual private users can be difficult to provide in certain aspect at times.


There are many ways to build more specific software implied to operate in the web realm. In any case, an answer to the question - ‘How to ultimately understand which model is the most optimal for my particular piece of software?’ should be based on one factor - the best possible capabilities of user service (due to request processing speed, content delivery speed, high-load servers’ availability, etc.). Planning the development of your new web app or looking for a team of experts to implement it? Look no further. A huge experience our dedicated specialists possess combined with a constant individual boost of qualification they get allows us to deliver a solution of any complexity at the most reasonable costs. Contact us right now - we’ll discuss all the details and get to work in the shortest terms.
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