I love sqlite's FTS. I have a number of personal projects where I have an archive of data and want to occasionally be able to do ad-hoc searches over and get reasonable ranking and results. Throwing sqlite fts at the problem gets me that in just a few lines of code.

You can even combine it with a sqlite vfs[0] to run full text searches against a sqlite db stored in s3 relatively efficiently.

[0]: https://github.com/psanford/sqlite3vfshttp