20 Years of Websites Evolution: Part 11 – Availability

In the previous chapter, we learned that Reliability helps us to ensure the system will work correctly even in a case of data corruption or component failure. But even if the system will work correctly for one user doesn’t mean it will still work nicely when many users want to join in. **Availability** measure how *available* is the system for everyone who wants to use it. High availability systems can offer the same smooth experience regardless of how many users simultaneously use them or where they are on the planet.
Availability and Reliability usually complement each other, but they can be mutually exclusive. A system can offer great reliability for a fixed number of users, but may be limited to the maximum total/concurrent users or suffer from degrading experience. High availability system can support many users at the same time without affecting performance, but even a small malfunction can bring the entire system down. This is why often the Reliability and Availability aspects of the system supplement each other in order to deliver the best possible system stability at scale.

20 Years of Websites Evolution: Part 10 – Reliability

Many times developers (and sometimes even project managers) think of a site as a “product”, which means once it’s live in production they can stop thinking about it and move to the next project. But in fact, websites are more like *services* and keeping them working as expected in the long-run is a full-time job and where the real challenge starts.
Keeping the site running usually falls into IT department, although in recent years it became more of a combined effort (this is the topic of the next chapter, Delivery).
It can be divided into 3 parts: Reliability, Availability, and Delivery:

20 Years of Websites Evolution: Part 8 – Legal & Ethical Consideration

Over the past 20 years, sites usage has become mainstream and many people were starting to depend on them for their daily activities. As more people were starting to use them, they had a real effect on people life. And this is when sites started to develop some darker practices. From email spam to users privacy violation and even using psychology in order to trick people into doing things they wouldn’t normally do, companies began abusing their powers and the trust of their users.
This is when it was apparent that some kind of regulation had to be made, and that regulation and how it affected site design is the topic of this chapter.

20 Years of Websites Evolution: Part 4 – Data Integration

Besides pages content, sites usually show data which was produced inside the company – for example, products catalog, customer information or statistical data. That data can be the result of another internal system or even entered manually into a file, but often some kind of processing was required in order to transfer it into the site database.
Finding out how to automatically move data from one system to another is the topic of this chapter.

20 Years of Websites Evolution: Part 3 – Dynamic Pages

In the previous part we saw how the systems which supported website publishing evolved during the years. But that evolution, which ended with CMS products, only effected those who create and maintain the sites, and site visitors were not aware of it. But there was another technological evolution that occurred simultaneously which had greater impact on the them, since it happened in their own browsers. This is the Client Side Evolution.