OpenWiFiMap is a database and map for free network WiFi routers (freifunk and others, too!).
This is the database/backend part of the openwifimap. Make sure to also take a look at its web frontend, the openwifimap HTML5 app.
The original backend was written in Javascript using CouchDB. Since maintaining that was problematic, it was rewritten in 2020/2021 to use Python/FastAPI/PostgreSQL.
See the Swagger API docs at /docs on the running backend (at api.openwifimap.net/docs, for example).
The somewhat more verbose old API doc can be found in the old API.md.
openwifimap is licensed under the MIT license.
The backend is basically keeping a list of JSON documents on disk which can get queried and updated via a web API. The database is used as search index only. PostgreSQL is total overkill for this but ¯_(ツ)_/¯
The interesting part of the code is in restapi.py.
In case you wonder, endpoint definitions are a bit complicated (BaseModel, response_model, Field, Query, ...) since FastAPI can generate nice Swagger API docs from this.