When we talk about checking bottlenecks in Magento backend implementations we often mention the built in profiler that allows to see loading time of particular backend functional elements. There are two general factors of such bottlenecks: heavy (or repetitive) database calls or slow PHP operations such as loops and similar cases.
In the beginning, Magento was one of the biggest PHP applications. The main purpose of that platform was to cover all needs of store owners being universal and flexible. So, Magento store owners got a big and interesting e-commerce platform and the developers got a big “battlefield” for their implementations. A lot of things have been changed from year to year: servers became more powerful, Magento much faster and the number of platforms, developers and extensions has grown significantly. As a result, every store owner has a wide choice of the solutions that might be implemented for their stores. Unfortunately, very often it’s hard to predict how good is some add-on for a specific Magento installation because of different reasons. You are installing first, tenth, thirtieth extension and then realize: the store is much slower than it was before.