Fun fact: SQLite is the most deployed and most used database. There are over one trillion (1000000000000 or a million million) SQLite databases in active use.

It is maintained by three people. They don’t allow outside contributions.

It is everywhere

SQLite is likely used more than all other database engines combined. Billions and billions of copies of SQLite exist in the wild. SQLite is in:

• Every Mobile (Android, iOS, Windows) device
• Every Mac or Windows10 machine
• Every Web browser
• Every instance of Skype, iTunes, and Dropbox client
• PHP and Python
• Most TV, set-top cable boxes and automotive multimedia systems
• Countless millions of other applications

How do they cook?

There are over 600 lines of test code for every line of code in SQLite. Tests cover 100% of branches in the library. The test suite is extremely diverse, including fuzz tests, boundary value tests, regression tests, and tests that simulate operating system crashes, power losses, I/O errors, and out-of-memory errors.

This writing is not my own. The first section is a rehash of the words from SQLite Most Deployed page. The testing section paragraph entirely taken verbatim from SQLite: past, present, and future paper.