SQLite is a self-contained, high-reliability, and very very fast SQL database engine. It’s known as the most widely deployed database engine in the world. It’s absolutely the most deployed database engine off-world, too.
There’s a really cool blog post about hosting SQLite online, with a virtual file system that uses range requests to cut down on fetches. In this way, you can read from a database of nearly any size and query it efficiently! With a properly written query you can do instant lookups against gigabyte+ SQLite tables.
If you mix this with trigram indexing you can do a lot of Full-Text search needs via an S3 bucket and the web! While it won’t have nearly as many features this could potentially replace quite a lot of the features Algolia provides.
Would I suggest replacing a mission-critical log aggregation and query for a top-100 tech company? Nope. Is it good enough for smaller use-cases? You betcha it is.