Why maintenance testing is so important?

After months of development, we have our lovely product ready. Go live is around the corner but does this means that our job as a QA is done? Not yet because we should plan also maintenance testing. A good example of what may happen if we don’t perform such one is otodom.pl. One of biggest in Poland in 2020 mortgage search pages. Total estimated number of impression on this site is over 14 millions yearly. They are already during a process of changing backend and migrating it to new version. But they completely forgot about existing users and existing functionalities! For many weeks, email notification was not working because of code changes. After another week or two, they added information that they are turning off the feature because of that change. Funny thing is that everything is on the production environment. The screenshot is in Polish language because they are only having localized Polish version. Maybe you still can see this issue on production. Here is the link: https://www.otodom.pl/pl/zapisane/wyszukiwania of course you will need an account on that page.