How to create a product filter with a minimum load?

Question

Database

Good afternoon. I'm working on a product filter module. How to make efficient filtering with minimal server load?
Details:
1. There will be 100-200 thousand products
2. There will be about 50-100
categories 3. Each category should have its own filter with 10-20 parameters (for example, color, size, price, in stock or not, and other product parameters inherent in this category only). The parameters are divided into points (that is, in the parameter the color will be, say, checkboxes with white, red, black, etc. points)
4. The filter will be on ajax. When you select an item in any parameter, the number of products with marked items of the entire filter is counted.
And the block should display how many products are in this selection.
Actually, I'm not interested in layout, ajax or php, the question is how to select from the database, while with minimal server load? How to interact with the base, or is it better to go the other way?
Please share your ideas.
Thanks :)