because it's faster to serve the full fidelity track, with all sensor data for every lat/lng pair, straight from disk as a gzipped file. I can store a point reduced version in postgis for actual geo operations, since that only needs lat/lng pairs, and not at 1hz sampling.

Pulling 21k points (1.8mb of JSON) for a single recording out of disk into memory, turning it into JSON, sending it over the wire to the client, is slow (500ms just to query, pull off disk and turn into JSON). Serving the same data pre-compressed, is 2ms. This isn't even considering what it takes nginx to compress it on the fly for every request.