In other words, you are unlikely to know up front whether an optimisation will be of any real benefit. Just write the code the simplest way. If, eventually after profiling you discover a bottleneck optimise that.from Optimize Later
(Also related: Premature Optimization)
I am currently designing an app that will make heavy use of the WordPress.com REST API. During the process I was a bit worried that the app will need to make multiple API requests at once and becomes too slow. But it seems like it’s no use worrying about now. We’ll have to see how the actual app runs, and work on optimizing it if it’s ever needed.