Hi, I'm Koschei

I’m based in Hefei, China, working on databases and systems — mostly in C++ and Rust.

My interest in storage engines and query execution grew out of competition. I entered the database track of China’s National Collegiate Computer System Capability Challenge twice: 21st out of 382 in 2023, then rebuilt the whole thing and placed 2nd out of 325 in 2024. Most of the year in between went into understanding why the first version was so slow.

Lately my attention has shifted toward language models. I’m working through Stanford’s CS336, building a language model and its inference stack from scratch, and placed 9th out of 703 in the DataAgents track of KDD Cup 2026. I also write tools when something annoys me enough — like ipatool-rs, an App Store CLI in Rust.

This blog is where I write down what tripped me up: a build of Doris that wouldn’t compile, a tokenizer that ran six hundred times too slow, an assignment spec I couldn’t parse. I write mostly to force myself to think clearly; if it happens to help you too, all the better.