Problems / Agents and tools, hard
Agent jobs are queued and run by workers. When an acknowledgement is lost, the queue redelivers and the job’s side effect (sending an email) happens twice.
Free to open. Runs in your browser, no sign-up.
No duplicate side effects.
30 requests a second for 30 seconds: 100% job (writes).
What each component does in this design, and what calls it. The simulator mimics each one from these settings.
| Component | Its job here | Settings |
|---|---|---|
| Load balancerLoad balancer | Traffic enters here.Calls Agent API.Layer 4 balancers route by IP and port; layer 7 balancers read HTTP and can route by path or header. | – |
| Agent APIApp service | Load balancer forwards to it.Calls Agent job queue (publishes).Little's law: throughput ≈ concurrency ÷ latency. 200 slots at 50 ms serve about 4,000 req/s. | 3 replicas × 500 slots · timeout 30 s |
| Agent job queueMessage queue | Agent API publishes to it.Calls Agent workers.If a consumer does not finish within the visibility timeout, the message is delivered again. | – |
| Agent workersWorker | Agent job queue consumes from it.Calls Email tool.Queues deliver at least once, so a worker can see the same message twice. | 32 concurrent jobs |
| Email toolTool / MCP server | Agent workers calls it.Tools give the model actions such as search or database queries; each call is another round trip. | 200 slots |
Try it first. Open one hint at a time if you get stuck.
At-least-once delivery means redelivery.
Make the job idempotent.
Store an idempotency key with each side effect.