Orchestration & Human-in-the-Loop

Orchestration coordinates steps, systems, and people on a timeline with clear ownership, SLAs, and evidence. Human-in-the-Loop (HITL) inserts judgment where rules or confidence are not enough. Design the flow first; automate stable parts; keep one source of truth.

Overview

Orchestration uses a central “conductor” to call tasks, enforce order, and track state. Choreography lets services react to events independently. Use orchestration when steps, deadlines, and approvals matter; use choreography for loosely-coupled signals with minimal coordination. Model the human and system steps in BPMN 2.0, with decisions in DMN and case work in CMMN.

When to orchestrate (vs. choreography)

Pick orchestration when…

  • There are approvals, SLAs, deadlines, or human reviews
  • Steps must run in strict order with compensation rules
  • Executives need a single place to see status and evidence

Pick choreography when…

  • Independent services react to events with weak ordering
  • Loose coupling matters more than central control
  • Temporary failure can be handled locally

Hybrid

Central orchestration for the critical path; event choreography for peripheral updates (notifications, analytics).

Core components

Orchestrator

  • Workflow engine/state machine; correlation IDs and timers
  • Compensations, retries, timeouts, and escalation hooks

Workers

  • Stateless, idempotent handlers; safe to retry
  • Access via allowlisted tools/APIs; role-scoped credentials

Queues & storage

  • At-least-once delivery (AMQP, Kafka) with DLQs
  • Idempotency keys; exactly-once semantics via design
  • Audit-grade state store; immutable logs

Patterns (saga, retries, idempotency)

Saga & compensation

  • Split long transactions; define compensating steps for partial failure
  • Prefer logical undo over database-level XA

Retries & backoff

  • Exponential backoff + jitter; cap retries; send to DLQ
  • Timeouts and circuit breakers for unstable dependencies

Idempotency

  • Use correlation/idempotency keys; ignore duplicate work
  • Design handlers to be repeat-safe (HTTP semantics: RFC 9110)

References

Routing, queues & SLAs

Work routing

  • Queues by priority, skill, region; FIFO within class
  • Assignment: round-robin, load, or skill-based
  • Limit WIP to protect lead time (Little’s Law)

SLAs

  • Define per step; timers and escalations; visible aging
  • Auto-reassign stuck work; notify owners

Metrics

  • Lead time, queue time, throughput, first-pass yield
  • Backlog aging; reassignments; breach counts

HITL design & thresholds

Thresholds

  • Confidence × impact grid: auto-approve, review, block
  • Dual-control for high-risk steps (four-eyes)

Reviewer UX

  • Show sources, diffs, and suggested actions
  • One-click edits; capture rationale; next-best steps

Workforce management

  • Queue sizing and shifts meet SLA windows
  • Sampling of “auto” decisions for quality
  • Feedback loops to improve rules/models

Evidence, audit & controls

Logging

  • Who did what, when, to which record (user, timestamp, object)
  • Immutable/tamper-evident logs; retention by policy

Controls

  • Segregation of duties; thresholds and approvals
  • Change control for workflows, bots, and integrations

References

Observability & SLOs

Tracing & metrics

  • Distributed traces across orchestrator, workers, and queues
  • SLIs: success rate, latency, error types, retries, DLQ size

SLOs

  • Targets for latency/success; error budgets to govern change pace

References

90-day starter

Days 0–30: Model & scope

  • Draft BPMN L2/L3; list approvals and SLAs
  • Pick orchestrated vs. choreographed segments
  • Define compensations and idempotency keys

Days 31–60: Build & guard

  • Implement retries, backoff, DLQ; add correlation IDs
  • Add HITL thresholds and reviewer UX
  • Wire tracing; set SLOs; create runbooks

Days 61–90: Pilot & prove

  • Pilot one corridor; track lead time, breach rate, rework
  • Fix hotspots; publish deltas; plan scale-out

References

Coordinate the flow. Route the edge cases. Keep evidence tight.

If you want an orchestration checklist (saga, retries, idempotency, HITL, SLOs), ask for a copy.

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