Valentyn KitI build the Rust core of a self-custody wallet and rebuild the layer underneath from scratch — databases, TCP servers, storage engines — to understand how the real ones work. This is where I write it down.https://valentynkit.com/Framework knowledge evaporates. Low-level knowledge compounds.https://valentynkit.com/blog/framework-knowledge-evaporates/https://valentynkit.com/blog/framework-knowledge-evaporates/I learned async three times before it clicked. Building a TCP echo server from blocking sockets up through kqueue and epoll in C, seven times, is what finally fixed it.Thu, 25 Jun 2026 00:00:00 GMTFrom one blocking accept() to epoll: a C TCP server up the I/O ladder, measuredhttps://valentynkit.com/blog/from-blocking-accept-to-epoll/https://valentynkit.com/blog/from-blocking-accept-to-epoll/Building a TCP echo server in C seven times, from blocking through select, poll, kqueue, and epoll, with the cost of each wall measured: a 1.5 second stall, a pegged core, the FD_SETSIZE ceiling, and O(ready) dispatch.Tue, 30 Jun 2026 00:00:00 GMTRust's compile errors are other languages' production bugshttps://valentynkit.com/blog/rust-compile-errors-are-production-bugs/https://valentynkit.com/blog/rust-compile-errors-are-production-bugs/Four Rust compiler refusals, each traced to the silent bug it prevents in Python, JavaScript, or C: float sorting, string indexing, integer overflow, lazy iterators. Plus the one place Rust stays quiet.Wed, 08 Jul 2026 00:00:00 GMTWhat Linux actually does when you read a filehttps://valentynkit.com/blog/what-linux-actually-does-when-you-read-a-file/https://valentynkit.com/blog/what-linux-actually-does-when-you-read-a-file/I asked for one 4 KiB page and got four back. The same read one page over gave me one.Fri, 07 Aug 2026 00:00:00 GMTYou don't understand a system until you've rebuilt ithttps://valentynkit.com/blog/you-dont-understand-a-system-until-youve-rebuilt-it/https://valentynkit.com/blog/you-dont-understand-a-system-until-youve-rebuilt-it/Using a system teaches its interface and reading its source teaches its mechanics, but only rebuilding a worse version teaches the constraints, which is where understanding actually lives. Why reconstruction works, and how to build a toy that teaches you something instead of lying to you.Wed, 22 Jul 2026 00:00:00 GMT