Intro
Learn internals by writing a Database Management System (DBMS) from scratch
https://build-your-own.org/blog/20251015_db_in_3000/
It covers:
- B+tree data structure.
 - Append-only KV.
 - Practical KV with a free list.
 - Tables on KV.
 - Range queries.
 - Secondary indexes.
 - Transactional interfaces.
 - Concurrency control.
 - SQL-like query language