HTMLy has a built-in search feature and related posts. I use file-naming convention than the speed always fast even though let say the blog has about 3k of post

HTMLy has a built-in search feature and related posts. I use file-naming convention than the speed always fast even though let say the blog has about 3k of posts with hundreds of tags, why? HTMLy don't read the content first but filter it first. I already test it with mini VPS (RAM 128 MB) and no speed penalty.