What is an application server?

Application servers have become a critical tool for many modern enterprises, enabling teams to build and start web applications, optimize app performance and create stronger end-user experiences for their customers.

Application servers play an important role in the development of software applications, connecting the user interface to critical information contained in backend databases. Most high-performing applications depend on app servers for running application logic and improving efficiency and management.

The global market for web application servers has grown considerably in the last 30 years and is expected to continue to grow over the next decade. According to Straits Research, it’s market size was valued at USD 14.9 billion in 2020 and is projected to reach USD 52.12 billion by 2030, a compound annual growth rate (CAGR) of 13.34%.¹

It has also become more diverse, including free open source platforms like Apache—which powered more websites than any other server in the world until 2014²—and more complex, enterprise-grade solutions from IBM and Oracle.

Because the market for application servers is so broad and varied, businesses have a wide range of factors to consider when selecting one that fits their needs. The most important considerations are the demands of application they wish to build, available resources, business needs and their preferred programming language.

Today, application servers play an important role in the development of many software applications, connecting the user interface to critical information contained in backend databases, such as the server-side application code.

In a business application, such as a financial services app or an equipment monitoring app that relies on the Internet of Things (IoT), the application code represents.

Business logic is logic that is applied to help an application carry out critical operations such as transactions or calculations based on business rules. It typically defines compute tasks and the order in which they are carried out. 

More broadly speaking, application servers help streamline app development, improve application performance and security, and enable a more consolidated management approach. Here’s a closer look at some of their benefits:

App servers help optimize many widely used application features, such as caching and request/response (r/o), which helps increase the overall efficiency of an application.

Application servers make it easier for programmers to build applications by delivering many built-in services and code libraries to handle common tasks, shortening time-to-market.

App servers give developers the tools and interfaces that they need to build and deploy a wide range of business applications from a single platform.

Due to their ability to handle concurrent requests, application servers are considered highly scalable business solutions. Many app servers have load-balancing capabilities, allowing them to distribute compute tasks across multiple nodes and help ensure peak performance even when traffic is high.

Application servers are often connected to access management systems, giving businesses the ability to control permissions using a wide range of security features, including authorization, authentication and data encryption.

Most application servers are highly flexible and can support multiple programming languages. Popular programming languages supported by web application servers include Java, ASP, .NET, PHP and others.

At their most basic, application servers provide the functionality and ecosystem in which a dynamic web application runs. Part of this functionality involves the hosting of the parts of an application known as middleware—software that connects components in a distributed network. App servers and the middleware they host help streamline application development and shorten development cycles by connecting platforms that initially were not designed to connect.

Application servers work closely with web servers, which are servers that deliver static content, such as HTML pages, images and videos. Often, a web server receives a hypertext transfer protocol request (HTTP) from a web page or web browser that directs it to an application server to process business logic. To increase their scalability, application servers rely on a capability known as multithreading so they can handle multiple client requests at once.

Multithreading is a process that helps ensure applications remain high-performing in times of high traffic. A server’s operations are broken down into routes known as threads. Multi-threading allows for a server to create and run multiple threads to fulfill a request simultaneously.

For example, if a user submits a request that requires an external resource to be accessed, such as a database, the application server uses separate threads (or operations) to respond to the request, enabling it to fulfill more than 1 client request at a time. Because most web servers don’t support multithreading, application servers play a critical role in making modern web application development scalable.

Because web application development is a highly complex environment, it’s critical that all aspects and processes be highly monitorable. From runtime engines such as Java and .NET to workloads and the responsiveness of individual components, monitoring is a critical part of application server functionality. Here are some ways application server monitoring helps ensure functionality and high performance.

Issue resolution: Application server monitoring detects changes in response times, CPU and memory usage, network throughput and more to spot problems so they can be fixed before they disrupt an application’s availability.

Resource allocation: Application monitoring helps developers spot opportunities to fine-tune configurations and adjust resource allocation for optimal performance.

Forecasting: With continuous monitoring, application servers can forecast for extra resource requirements that will be needed during times of high traffic, helping to avoid disruption.

Application servers are closely related to web servers, and the two terms are often used interchangeably. Technically, this isn’t correct, as web servers are actually a subset of application servers. However, the differences between web and application servers have become less important as the technologies continue to merge.

Today, many application servers utilize web server capabilities and vice versa, using HTTP and its common variants as their primary communication protocol. In fact, many web servers (and even some application servers) are now referred to as web application servers. Here are some similarities and differences between the two that are worth taking into consideration when assessing their value to your business:

As app development has become a critical piece of digital transformation, many businesses are turning to web application servers to help them build, start and run business applications. Here are five of the most widely used application servers and the core capabilities that make them appealing to enterprises.

Apache Kafka HTTP Server, more commonly known as "Apache," is an open source web application server first released in 1995 when smartphones and the demands of mobile application development were still at least a decade away. Apache’s many strengths include usability, add-on features that are easy to install, customizable code and high performance.

Like Apache, NGINX is a free, open source web server and shares many of the same capabilities, such as ease, customizability and high performance. However, NGINX is unique in that it acts as an all-in-one load balancer, reverse proxy, web server, content cache and application programming interface (API) gateway. For example, NGINX has a connectivity stack for the popular container orchestration platform Kubernetes that helps developers scale, monitor and manage applications in the cloud.

Like Apache and NGINX, Glassfish is another open source application server. Started in 2006 by Sun Microsystems, Glassfish is an exclusively Java Enterprise Edition (EE) application server, meaning it implements Java EE platform APIs and provides standard Java EE services. Glassfish supports Java Servlets, Enterprise JavaBeans (EJB) and others. It also works well as a web server, delivering content in response to HTTP requests from a web browser. Using Glassfish, developers can build business applications that are highly scalable and efficient and will work seamlessly with legacy technologies.

Like other enterprise-grade web application servers, IBM WebSphere enables many high-performing applications that enhance business logic and help deliver more value to customers. IBM WebSphere accelerates app delivery and allows developers to focus more closely on code and business logic rather than infrastructure management. In addition to these benefits, WebSphere also helps increase performance, reduce costs and improve time to value of business applications. WebSphere empowers teams to build new cloud-native apps and modernize existing ones, all while maintaining the traditional WebSphere estate.

Like WebSphere, WebLogic is a platform that was created for the development of enterprise applications. The server provides a robust implementation of Java EE and Jakarta EE and can support on-premises and cloud ecosystems. Oracle WebLogic was also created with Kubernetes in mind. WebLogic Kubernetes ToolKit is an open source toolset that helps streamline running apps on Kubernetes whether the server is on-premises or in the cloud.