I could say speed, but the main reason for me is because it is fun. And I like to see what I can make C do. :D

"Because I can" remains an entirely legitimate reason for a hobby project.

If anything, you've gone further along the "also (at least sort of) practical" scale than I expected.

Given as mentioned elsewhere a per-request arena + bump allocator system, it might actually be -genuinely- practical (to the extent that writing application logic in C is at all ;)

Bravo.

The second point is absolutely fair and your project is very cool and impressive, but the speed one is misleading. I am fairly sure you actually leave a fair bit of performance on the table simply by how convoluted parallelism and async IO are in C, and something like Java might easily outperform it in standard CRUD backend use cases.