If you can’t see it, it’s not exist.

not Blender specific

I’ve come across many newbie’s project with quite heavy scene.
They would cry how slow their project would render.

One common mistake is that they place objects everywhere, like real world objects, even where the camera never sees.

So, if the object or its reflection, or shadow is not subjective in the camera’s field of view, it rather not exist at all – delete it! And make the set as small as possible.