Mailing address:SIA Monkey See Monkey Do
healthchecks.io is an open source project. The code is on GitHub, it has BSD license, and is accepting contributions.
The service is currently run on Hetzner bare metal servers, with healthy excess capacity to handle traffic spikes. The app servers are load balanced. The PostgreSQL database has a hot standby as well as full daily backups to S3. The database fail-over process is manual, and the ops team consists of a single person, so multi-hour or even multi-day outages are possible! More details.
While we can only guarantee a best effort availability, in practice the availability has exceeded 99.9% since the service publicly launched in July 2015.