Vercel Queues

Implement queue producers and consumers using Vercel Queues docs and SDK contracts.

Step 1: Classify the request

Choose one path before writing code:

If the task spans multiple categories, read only the relevant files above.

Step 2: Apply core guardrails

1. Design consumers as idempotent because delivery is at-least-once.
2. Pick push mode by default on Vercel unless the task explicitly needs scheduled/batched/client-driven polling.
3. For poll mode, pin an explicit region and use the same region for send and receive.
4. Use bounded retry strategy for poison messages (acknowledge: true after threshold).
5. Keep topic and consumer names within ^[A-Za-z0-9_-]+$.

Step 3: Implement with minimal surface

1. Prefer top-level send and handleCallback for standard Vercel push mode.
2. Use QueueClient only when you need custom options (transport, token, headers, deploymentId).
3. Use PollingQueueClient for poll mode (receive) and handle { ok: false, reason: "empty" } explicitly.
4. Keep vercel.json trigger mapping explicit and scoped to the consumer route.

Step 4: Validate behavior

1. Verify producer returns messageId and treat nullable messageId as acceptable deferred acceptance.
2. Verify consumer behavior across success, retry, and poison-message paths.
3. Verify visibility timeout assumptions match workload duration.
4. Verify region assumptions in poll mode.

Step 5: Troubleshoot from first principles

1. Authentication issues: check OIDC/token source and env loading.
2. Missing deliveries: verify topic name, trigger registration, and region alignment.
3. Duplicate processing: verify idempotency key strategy and consumer idempotency.
4. Backlog growth: inspect consumer throughput, retry policy, and visibility timeout.