2. Error Rates

Errors in web applications refer to the fallacies that happen while processing users’ requests. Respectively, the error rate is defined as the percentage of these error requests compared to the total number of requests and is a key indicator of the application's overall performance failure.

They can be caused by many different things and are rather unavoidable, but making sure they happen as rarely as possible is a very important part of keeping our users happy. As a matter of fact, statistics show that 75% of users leave applications and websites after only one software error, but only 1% of them actually report the problem to the company.

So, finding the problems before our users do is pretty much what we’re trying to do here, and the best way to do this is by using Real User Monitoring (RUM) tools which continuously check our system's availability, functioning, and responsiveness. RUM allows us to observe exactly how our users engage with our website or app and it provides us with a deep, top-down view of a wide range of front-end browser, backend database, and server-level issues that they might experience. Some of the most popular RUM tools are:

• Sematext Experience
• Dynatrace RUM
• AppDynamics Browser RUM
• New Relic Browser
• Pingdom

One thing that we should always keep an eye on is the behavior of the site under different loads; having a larger number of users than its capacity is the main cause of the increased error rate.