Explanation

For a broader introduction, there are also slides from a 2025 presentation about Triple Pat given at The Hacker Building.

• One mechanism, many names — Watchdog timers, heartbeats, dead man's switches, snooze buttons, fire drills, and check-in timers are mostly the same idea. How the names map, and why we say check in.
• Design of the checkin service — The design of the Triple Pat checkin and monitoring service
• What makes Triple Pat reliable? — What reliable means for a check-in, how we are set up for success, and our track record
• Why synthetic alerts fire at random — Why the synthetic alert libraries schedule firings at random, why that randomness is Poisson, and why it is bounded