Whether you prefer desktop or mobile applications, we all rely on these web-based apps in one way or another. From editing documents on Google Docs to checking Instagram, we all use applications every day for work, leisure and communication.

Our reliance on these applications is only set to increase. In fact, the global application server market size was estimated to be $20.06 billion in 2022, and it’s expected to grow at a compound annual growth rate (CAGR) of 13.9% from 2023 to 2030.

But what exactly is an application server, and why are they necessary for supporting applications? Discover more about application servers, how they work and their advantages in this comprehensive guide.

What is an application server?

An application server is a server that hosts and operates applications, supporting their development and delivery. When an end user or client sends a request to access an application, the application server communicates with the web server and the database server to deliver a dynamic and customised response.

The application server sits within a three-tier system on the server side, with the web server closest to the client, the database server furthest from the client and the application server in the middle. As such, the application server functions as middleware, mediating between the web server and the database. 

When someone tries to access an application, the client device (e.g. their computer) is on the client side, and it sends an HTTP request to the web server to retrieve the application. The web server then communicates with the application server to process this request, and the application server retrieves the application’s data from the database via a servlet request and response – servlet is a programming language class used by the application server and database. Once the application server has processed the data to load the application’s dynamic content, it responds to the web server via servlet. The web server translates this response to an HTTP format so the client device can access it.

Web server vs application server

So, why can’t this process be handled by the web server? Why is the application server necessary?

Web servers are perfectly capable of handling HTTP requests from clients and processing static data. So if you try to load a web page that contains static information, a web server is powerful enough to process this static data request and allow you to access the website.

However, if you decide to access an interactive tool, this will need to be handled by an application server. Dynamic requests, such as those from applications, need the superior power of an application server so that a dynamic, customised response can be delivered to the end user. This is why applications require a three-tier program architecture: a web server, an application server and a database. 

The application server retrieves the app data from the database server and delivers the application, and the web server communicates with the client via an HTTP format to ensure that the application is accessible.

How does an application server work?

We’ve already briefly discussed what an application server is and how it delivers applications to users, but let’s break down the process to examine each step:

  1. The client requests access to an application with an HTTP request via their web browser.
  2. As the request is for dynamic data, the web server receives this request and passes it on to the application server.
  3. The application server turns the HTTP request into a servlet request and sends it to the database.
  4. The database server retrieves the necessary data and sends a servlet response back to the application server.
  5. The app server receives the servlet response and translates it into an HTTP response that’s accessible to the end user.
  6. The web server receives this HTTP response and passes it on to the user, allowing them to access the application.

Processing this dynamic web content request without an application server isn’t possible. Application servers are powerful servers that fill in a gap to deliver applications as quickly as possible for end users – this boosts website performance and keeps users happy.


Performance can be improved even further if the application servers implement caching.

Caching is a method of reducing the amount of server-side processing needed to deliver a website or application by storing relevant data in RAM (random access memory). Usually, to load an application, the application server must repeatedly request data from the database server, which can make the whole process slower. However, if the application server stores some of the frequently accessed data in a cache, this data can be retrieved instantly when a request is received rather than having to wait for the database server.

What are the benefits of application servers?

Application servers help users access applications quickly, but this isn’t their only benefit. Here are some more advantages of application servers:

1. Better traffic optimisation and processing

Application servers help web servers handle and process more traffic and requests, allowing users to access content more quickly. Even under high traffic loads, application servers are excellent at processing simultaneous requests, so web users will continue to be satisfied with the service they receive. When web servers are unable to process large numbers of requests or requests for dynamic content, application servers can step in to relieve some of the workload and keep all processes running smoothly.

2. Enhanced security

Another fantastic benefit of application servers is that they can enhance server security by adding another layer between the client-facing web server and the database server. This provides extra protection for the confidential data stored in the database, as malicious web communications will be less likely to infiltrate the database server. 

In particular, application servers are very good at thwarting SQL injection attacks. An SQL injection is a type of cyber attack where malicious SQL code is injected into an application to allow the attacker to view or edit a database. SQL (structured query language) is a programming language that manages data stored in databases.

3. Load balancing

Application servers also improve performance by providing load balancing. Load balancing is a method of distributing network traffic across multiple servers, which means that none of the servers become overloaded and compromised. Since none of the servers are overworked, optimum performance is achieved and the lifespan of the servers is prolonged.

4. Fault tolerance and disaster recovery

Having multiple servers in your network architecture is essential for fault tolerance. Fault tolerance refers to a system’s ability to continue operating even when faced with failures or malfunctions in the hardware or software. Since application servers are part of a three-tier system, they can help improve fault tolerance by adding more layers to the system and ensuring that one server isn’t handling the entire workload.

By improving fault tolerance, application servers can aid your data protection and disaster recovery efforts. System failures can lead to catastrophic data loss, so preparing for these failures with redundant systems can protect your data or make it easier to recover.

Frequently asked questions about application servers

What does an application server do?

An application server supports the delivery of applications to end users. Web servers are capable of handling requests for static data, such as a regular web page, but if a user wants to access an application with dynamic data, an application server is needed to process this request and deliver dynamic, customisable content. The application server communicates with the web server and the database server in a three-tier network architecture to process requests, retrieve data and deliver the desired content to the end user.

Why do we need application servers?

Application servers are needed to deliver dynamic content (often in the form of applications) to users because these requests can’t be handled by web servers alone. Plus, application servers can enhance performance and security by adding another layer to the network architecture, which improves data protection and provides load balancing.

As we become more and more reliant on desktop and mobile applications, our need for application servers will only increase. The rise of cloud platforms and social media apps has been a huge contributing factor in the growth of applications and application servers.

What are the different types of application servers?

There are three main types of application servers. These are:

  • Active application servers or stateful servers – this server provides support in an environment where business logic is kept server-side (business logic is a type of programming that determines how data is shown, stored or altered, therefore handling the exchange of information between a database and end user).
  • Web information servers – this server helps create pages from a database using HTML templates.
  • Component servers – this type of application server allows software components to access a database, and it also supports transaction processing requests.

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