Server pages represented one approach to tackling the dynamic web server challenge, and one that was especially suitable for those web developers who primarily worked with static HTML, CSS, and JavaScript backgrounds.

For those that were already skilled programmers, the custom server approach provided less confinement and greater control. But it came at a cost - the programmer had to author the entire server. Writing a server from scratch is both a lot of work, and also introduces many more points where design issues can lead to poor performance and vulnerable web apps.

Thus, a third approach was developed, which leveraged existing and well-suited technologies to handle some aspects of the web app needs. We can separate the needed functionality into three primary areas, each of which is tackled with a different technology:

1. Serving static content
2. Creating and serving dynamic content
3. Providing persistent data storage

Serving Static Content

We’ve already discussed file servers extensively, and even discussed some options for optimizing their performance - like caching the most frequently requested files. There are a number of software packages that have been developed and optimized for this task. Some of the best known are:

• The Apache HTTP Server Project, an open-source server project originally launched in 1995, and consistently the most popular server software on the Internet. The CS department website is hosted on an Apache server, as is your personal web site on the departmental server.
• Internet Information Services (IIS), Microsoft’s flagship web server bundled with the Windows Server operating system.
• Nginx is also open-source, and intended to be a lighter-weight alternative to Apache HTTP.

Creating and Serving Dynamic Content

Creating and serving dynamic content is typically done by writing a custom application. As pointed out above, this can be done using any programming language. The strategies employed in such web server designs depend greatly upon the choice of language - for example, Node webservers rely heavily on asynchronous operation.

Some interpreted programming languages are typically managed by a web server like Apache, which utilizes plug-ins to run PHP, Ruby, or Python. Similarly, IIS runs ASP.NET program scripts written in C# or Visual Basic. This helps offset some of the time penalty incurred by creating the dynamic content with an interpreted programming language, as static content benefits from the server optimizations.

In contrast, other languages are more commonly used to write a web server that handles both static and dynamic content. This includes more system-oriented languages like C/C++, Java, and Go and more interpreted languages like Node.js.

In either case, the programming language is often combined with a framework written in that language that provides support for building a web application. Some of the best-known frameworks (and their languages) are:

• Express (JavaScript)
• Laravel (PHP)
• Flask (Python)
• Django (Python)
• ASP.NET (C#)
• Ruby on Rails (Ruby)
• Grails (Java/Groovy)
• Spring (Java)
• Phoenix (Elixir)

Providing Persistent Data Storage

While a file system is the traditional route for persistent storage of data in files, as we saw in our discussion of static file servers, holding data in memory can vastly improve server performance. However, memory is volatile (it is flushed when the hardware is powered down), so an ideal system combines long-term, file-based storage with in-memory caching. Additionally, structured access to that data (allowing it to be queried systematically and efficiently) can also greatly improve performance of a webserver.

This role is typically managed by some flavor of database application. Relational databases like the open-source MySQL and PostgresSQL, and closed-source SQL Server and Oracle Database remain popular options. However, NoSQL databases like MongoDB and CouchDB are gaining a greater market share and are ideal for certain kinds of applications. Cloud-based persistence solutions like Google Firebase are also providing new alternatives.

The Stack

This combination of software, programming language, along with the operating system running them have come to be referred to as a stack. Web developers who understood and worked with all of the parts came to be known as full-stack developers.

Clearly, there are a lot of possible combinations of technologies to create a stack, so it was important to know which stacks with which a developer was working. For convenience, the stacks often came to be referred to by acronyms. Some common stacks you will hear of are:

• LAMP (Linux, Apache, MySQL, PHP) - the granddaddy of stacks, composed entirely of open-source, free software packages.
• LEMP (Linux, Nginx, MySQL, PHP) - basically LAMP substituting the Nginx server for Apache
• MEAN (MongoDB, Express, Angular, Node) - Also entirely open-source

Microsoft has their own traditional stack ASP.NET, which is built on Windows Server (the OS), IIS (Internet Information Services, the webserver), a .NET language like C# or Visual Basic, and MSSQL. With the launch of .NET Core, you can now also build a .NET stack running on a Linux OS.

Additionally, frameworks like Django, Ruby on Rails, Express, Laravel, etc. often incorporate preferred stacks (though some parts, specifically the server and database, can typically be swapped out).