Decades ago, more specifically in 1974, Intel introduced 8080 to the world, which is an 8-bit processor with a 2 MHz clock speed and 64 KB of memory. This processor was used in Altair and began the revolution in personal computers.
It was sold pre-assembled or as a kit for hobbyists. It was the first computer to have enough power to actually be used for calculations. Even though it had some poor design choices and needed an engineering major to be able to use and program it, it started the spread of personal computers to the general public.
The technology evolved rapidly and the processor industry followed Moore's law, almost doubling speed every two years. Processors were still single core, with a low-efficiency ratio (power consumption per clock cycle). Because of this, servers usually did one specific job, called a service, like serving HTTP pages or managing a Lightweight Directory Access Protocol (LDAP) directory. Services were the monolith, with very few components, and were compiled altogether to be able to take the most out of the hardware processor and memory.
In the 90s, the internet was still only available for the few. Hypertext, based on HTML and HTTP, was in its infancy. Documents were simple and browsers developed language and protocol as they pleased. Competition for market share was ferocious between Internet Explorer and Netscape. The latter introduced JavaScript, which Microsoft copied as JScript:
After the turn of the century, processor speed continued to increase, memory grew to generous sizes, and 32-bit became insufficient for allocating memory addresses. The all-new 64-bit architecture appeared and personal computer processors hit the 100 W consumption mark. Servers gained muscle and were able to handle different services. Developers still avoided breaking the service into parts. Interprocess communication was considered slow and services were kept in threads, inside a single process.
The internet was starting to become largely available. Telcos started offering triple play, which included the internet bundled with television and phone services. Cellphones became part of the revolution and the age of the smartphone began.
JSON appeared as a subset of the JavaScript language, although it's considered a language-independent data format. Some web services began to support the format.
The following is an example of servers with a couple of services running, but still having only one processor.
Processor evolution then shifted. Instead of the increased speed that we were used to, processors started to appear with two cores, and then four cores. Eight cores followed, and it seemed the evolution of the computer would follow this path for some time.
This also meant a shift in architecture in the development paradigms. Relying on the system to take advantage of all processors is unwise. Services started to take advantage of this new layout and now it's common to see services having at least one processor per core. Just look at any web server or proxy, such as Apache or Nginx.
The internet is now widely available. Mobile access to the internet and its information corresponds to more or less half of all internet access.
In 2012, the Internet Engineering Task Force (IETF) began its first drafts for the second version of HTTP or HTTP/2, and World Wide Web Consortium (W3C) did the same for HTML/HTML5, as both standards were old and needed a remake. Thankfully, browsers agreed on merging new features and specifications and developers no longer have the burden of developing and testing their ideas on the different browser edge cases.
The following is an example of servers with more services running as we reach a point where each server has more than one processor:
Access to information in real time is a growing demand. The Internet of Things (IoT) multiplies the number of devices connected to the internet. People now have a couple of devices at home, and the number will just keep rising. Applications need to be able to handle this growth.
On the internet, HTTP is the standard protocol for communication. Routers usually do not block it, as it is considered a low traffic protocol (in contrast with video streams). This is actually not true nowadays, but it's now so widely used that changing this behavior would probably cause trouble.
Nowadays, it's actually so common to have the HTTP serving developer API working with JSON that most programming languages that release any version after 2015 probably support this data format natively.
As a consequence of processor evolution, and because of the data-demanding internet we now have, it's important to not only be able to scale a service or application to the several available cores, but also to scale outside a single hardware machine.
Many developers started using and following the Service-Oriented Architecture (SOA) principle. It's a principle where the architecture is focused on services, and each service presents itself to others as an application component and provides information to other application components, passing messages over some standard communication protocol.