Execution Model

1. Boot Sequence (Main.ts)

2. MQTT Message Processing Pipeline

3. Command Dispatch Lifecycle

4. WebSocket State Propagation

5. Background Job Execution

Job	Trigger	Interval	Implementation
Command Sweeper	setInterval	30s	Queries commands where status=dispatched AND created_at < cutoff. Batch updates to expired.
Heartbeat Monitor	setInterval	Configurable	Checks Redis TTL keys per device. If expired → marks device offline, triggers OTA check.
Email Worker	BullMQ consumer	Continuous	5 concurrent workers, 50/min rate limit, exponential backoff × 5 attempts. Dead-letter on exhaustion.
HX47 Health Check	setInterval	5s	Checks heartbeat timestamp gap. 3 consecutive failures → attempt restart with backoff (max 5).

6. Graceful Shutdown Sequence