The sensor's database is a text file it appends to over HTTP

An ESP32 on the roof reads temperature, humidity, and pressure once a minute. It makes one request: PUT /api/v1/files/roof/2026-09.csv?append with a single line as the body. The files service creates the file the first time and appends every time after.

That is the whole ingestion pipeline. No MQTT broker, no time-series database, no ingest function, no migration when you add a column; the board writes the column.

The analyst's notebook reads the same URL into pandas. The dashboard reads it with fetch. ?history shows when each line landed, and ?hash lets the nightly backup verify its copy. A month is a file; a year is a folder.

Forty-three thousand lines a month, forty bytes each, on a box you already rent.

The sensor's database is a text file it appends to over HTTP.