Leases and Fencing Tokens for Shared Resources

Two workers, one shared resource, and a worker that does not know it is late. This course covers time-boxed leases that expire without cooperation, monotonic fencing tokens that let the resource reject a stale writer, the clock-skew trap in naive expiry checks, correct behaviour when renewal fails, and why a scheduled run that crashes while holding a plain lock is worse than a run that never started.