SQLite is typically used only for development in web apps, but it is more than adequate for production for most apps. Glad to see Rails is working toward supporting SQLite in production:
Getting SQLite ready for production
On top of the trifecta of Solid adapters that makes it possible for SQLite to power Action Cable, Rails.cache, and Active Job, a bunch of work has gone into making the SQLite adapter and Ruby driver suitable for real production use in Rails 8.
At 37signals, we’re building a growing suite of apps that use SQLite in production with ONCE. There are now thousands of installations of both Campfire and Writebook running in the wild that all run SQLite. This has meant a lot of real-world pressure on ensuring that Rails (and Ruby) is working that wonderful file-based database as well as it can be. Through proper defaults like WAL and IMMEDIATE mode. Special thanks to Stephen Margheim for a slew of such improvements and Mike Dalessio for solving a last-minute SQLite file corruption issue in the Ruby driver.