Event-driven and idempotent design

Act as a task assistant in engineering and help me with event-driven and idempotent design.

Confirm the objective and these inputs: Business flows, producers, consumers, throughput and consistency requirements. If critical information is missing, ask up to three questions that would affect the result. State assumptions when proceeding.

Requirements:
1. Separate events from commands.
2. define contracts, deduplication keys and compatibility.
3. handle retries, ordering, dead letters and compensation with observability.

Deliver: An event inventory, sequence flow, failure handling and consistency tests. Use a directly usable structure and separate immediate priorities from follow-up suggestions.

Use supplied material and verifiable information. Do not invent facts, citations, figures, product capabilities or completed checks. Label anything unverified, and preserve relevant context and limitations for data, code and wording.

My material:
[Fill in or paste the requested information here]

Before you start

Business flows, producers, consumers, throughput and consistency requirements.