The latest articles on DEV Community by kimhjo (@hyeonjo00). https://dev.to/hyeonjo00 https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F3883826%2F0db217fb-7504-4156-a780-186e775b8164.jpg https://dev.to/hyeonjo00 en kimhjo Fri, 17 Apr 2026 06:58:00 +0000 https://dev.to/hyeonjo00/i-built-a-database-engine-in-pure-c-heres-what-i-learned-95o https://dev.to/hyeonjo00/i-built-a-database-engine-in-pure-c-heres-what-i-learned-95o <p>I recently built MiniDB Studio, a lightweight database engine in pure C (C11) <br> as a learning project. Here's what I ended up building and what surprised me along the way.</p> <h2> What it does </h2> <ul> <li>B+ Tree indexing on id and age fields</li> <li>Hash indexes for fast exact lookups</li> <li>WAL-style crash recovery with CSV snapshot replay</li> <li>A native desktop UI built with raylib</li> <li>A lightweight query optimizer for range scans and ordered traversal</li> </ul> <h2> The hardest part </h2> <p>Getting WAL replay to behave correctly after a crash mid-write was the <br> most painful part. The tricky case is when a write is partially flushed <br> before the crash — you need to detect the incomplete entry and roll back <br> to the last clean checkpoint without corrupting the rest of the log.</p> <h2> The architecture </h2> <p>The project is split into two layers:</p> <ul> <li>A reusable pure C storage engine library</li> <li>A separate UI binary that links against it</li> </ul> <p>Keeping them decoupled meant I could test the engine independently <br> without the UI getting in the way.</p> <h2> What I'd do differently </h2> <p>If I built this again I'd add a proper buffer pool manager earlier. <br> Right now reads go straight to disk more often than they should.</p> <h2> Links </h2> <ul> <li>GitHub: <a href="https://github.com/hyeonjo00/c-mini-db-engine" rel="noopener noreferrer">https://github.com/hyeonjo00/c-mini-db-engine</a> </li> <li>Whitepaper: <a href="https://github.com/hyeonjo00/c-mini-db-engine/blob/main/docs/minidb-studio-algorithm-whitepaper-en.pdf" rel="noopener noreferrer">https://github.com/hyeonjo00/c-mini-db-engine/blob/main/docs/minidb-studio-algorithm-whitepaper-en.pdf</a> </li> </ul> <p>Feedback welcome — especially on the storage engine design.</p> c database beginners programming