Code should work, but does not have to be efficient.
Don't worry about optimizing code. Rely on the computer to do the work. Compute or derive values when possible. When you have a small user base, a small amount of data and huge amounts of CPU available, performance isn't a concern. Why? Performant code tends to be much more complicated code and will slow down delivery.
This principle is useful for early phases of the Software Development Life Cycle (SDLC) such an MVP.