Building SQLite from Scratch: 740 Lines of C++23 to Understand Every Byte of a .db File

You fire up a MySQL client, connect to port 3306, send off your SQL, and the server parses, optimizes, hits an index, fetches rows, and packs the result back to you. You can picture that entire pipeline.

SQLite has none of that. No server process, no port, no wire protocol. Just a single file: my.db.

So the real question is — what exactly is stuffed inside that file that makes SELECT * FROM apples WHERE color='Yellow' return the right answer?

TinySqlite takes this apart across 740 lines of C++23. It doesn't link against the official SQLite library. It opens a .db file's raw binary and pries the data directly out of the disk bytes. We'll follow its code path, peeling back SQLite's file format layer by layer.

This article covers: file header → B-tree pages → varint encoding → the schema table → full table scans → index scans.