React is well known for being performant "out-of-the" box. Well, this is true but ... As an engineer, you've probably heard that latest version of a particular framework, language or feature is best in the class but then it turned to have problems. React is the same, if you write a code that is not optimised, React won't be able to works its magic in 100%. Possibly it still be fast, but it could be faster.
This short article will give you some useful, real-life examples on how shouldComponentUpdate can save re-rendering of components.