Apparently he used Sentinel-Hub, which is a service I'd never heard of. I just signed up to try their service but apparently the free plan advertised on their pricing page is a scam. There's no such thing. It seems you can't use the service without paying.
Though it’s a trade off! GOES has a really fast return (10-15 minutes, IIRC) but doesn’t do global and has comparatively poor spatial resolution (red at 500m per pixel, many near IR at 1km, LWIR at 2km). So you can get some data every 15 minutes, but for the city of San Francisco it’s only 10x10 pixels.
This is part of why folks like to join high-resolution data with high-temporal frequency data like GOES. Including me! (Well, I hope to get back to my side project using the Descartes Labs API to “learn” high-spatial GOES from the combo of sentinel2 and GOES).