Need help with ideas to construct a large interactive grid

I am a beginner with three.js and would like to know your thoughts on how to approach the below case.

I want to construct a large grid(potential 30k cells) that could have different colors for the cells. I need the cells to be interactive where users can select one or a range of cells. From initial reading, it occurs that I can’t have each cell be rendered by its own mesh which could be cause performance implications. But, I can’t find what the alternatives are.
Could you help with a solution please?

As a starting point, you can use this: How could be the best way of implementing an fft chart?