Last I heard they self hosted. Far as I understand it’s incredibly cheap for them to host. Especially since they’ve been completely cannibalized.

They have since been bought by private equity and brought on architecture astronauts who moved it to a cloud provider.

GCP and Cloudflare are mentioned on their status page.

They're strangely committed to serving up pointless jquery from a Google domain. I'm sure there's a revenue stream behind that.