Performance is an omnipresent topic in making real-time games. In order to create the illusion of moving images, we need a frame rate of at least 15 frames per second.
Depending on the platform and game, 30, 60, or even more frames per second may be the target.
Unreal Engine provides many features and they have different performance characteristics. In order to optimize the content or code to achieve the required performance, you need to see
where the performance is spent. For that, you can use the engine profiling tools. Every case is different and some knowledge about the internals of hardware and software is needed..
The Performance and Profiling pages linked below will guide you through profiling your project.