Meilisearch is an open-source engine with a RESTful API. Loosely following the Diátaxis framework, the documentation is a combination of tutorials, task-oriented how-tos, conceptual articles, and an API reference.
I maintained the Meilisearch docs together with Tommy Melvin and Maryam Suleiman for my first two years in the company. After internal restructuring, I became its sole maintainer.