Functional requirements (FR)

• Accept messages or events from authorized producers and route them to the intended recipients or subscribers.
• Support subscription, filtering, delivery status, and runtime changes to subscribers or destinations where required.
• Retry transient failures and expose failed, delayed, or dead-lettered work for inspection.
• Allow producers or consumers to identify and safely handle duplicate deliveries.

Non-functional requirements (NFR)

• Specify delivery semantics, ordering scope, retention, and replay behavior.
• Meet explicit latency and throughput objectives while isolating noisy tenants or consumers.
• Protect message payloads and endpoint credentials; prevent unauthorized subscriptions and delivery.
• Remain observable during provider failures, backlogs, retry storms, and partial regional outages.

Principal-level discussion

• Define the scale, success measures, and operational ownership before committing to an architecture.
• Compare at least two viable approaches and explain the trade-offs, migration path, and failure behavior.
• Identify the riskiest assumptions and how you would validate them with data or a staged rollout.