RabbitMQ Priority Queue Design Prompt

You are a senior platform engineer who has built RabbitMQ priority queues that behave correctly under load. Help me design mine so high-priority messages truly jump the line.

I will provide:
- The priority tiers I need and the traffic mix per tier (e.g., 5% urgent, 95% normal) [DESCRIBE]
- Whether low-priority messages must eventually be processed (anti-starvation requirement) [DESCRIBE]
- Consumer setup: consumer count, current prefetch, processing time [DESCRIBE]
- Expected backlog depth and broker version [DESCRIBE]

Your job:

1. **Pick the number of priority levels** — explain that each priority level adds overhead and that a small number (e.g., 2-3) is almost always enough; map my tiers onto `x-max-priority` without inventing ten levels I'll never use.

2. **Explain the prefetch interaction** — this is the killer: priority only orders messages WAITING in the queue. If a consumer has a high prefetch, it has already pulled a batch of low-priority messages into its local buffer, and a newly arrived urgent message waits behind them. Recommend prefetch = 1 (or very low) so priority is honored at delivery time.

3. **Starvation** — describe how a flood of high-priority messages can starve low-priority ones forever, and whether my requirement needs an anti-starvation mechanism (aging, separate queues, or rate-limiting the high tier).

4. **Single queue vs separate queues** — compare a priority queue against two plain queues with weighted consumers, and recommend which fits my mix.

5. **Validate** — confirm `x-max-priority` is set at declare time (it can't be added later), then load-test that urgent messages are processed ahead of normal ones with the chosen prefetch.

Output as: (a) the priority-level count with reasoning, (b) the declare arguments and the required low prefetch, (c) the starvation handling, (d) single-vs-separate-queue verdict, (e) the load test that proves priority works.

Load-test the priority behavior on staging with a realistic traffic mix and the production prefetch. Confirm urgent messages actually preempt normal ones — a high prefetch silently defeats priority, and that only shows up under load, not in a quick functional test.