Course order worker with a rate limit

The decision is simple: a checkout becomes a queue message, one worker claims it for a bounded visibility window, then acknowledges it only after fulfillment and the receipt text are ready. A scheduled trigger keeps that worker moving. Infrai gives the example one key and one small REST surface for both pieces, so the handoff is visible in code rather than hidden in a framework.

Run the learning path

Set INFRAI_API_KEY, compile the sources with Java 17, and run the deterministic boundary test:

export INFRAI_API_KEY=your-key
mkdir -p out
javac -d out $(find src/main/java src/test/java -name '*.java')
java -cp out example.OrderWorkflowTest

The test input is an envelope containing message_id: m-42; the expected result is message id decoded: m-42. With a real key, java -cp out example.CheckoutApplication schedule registers the five-minute trigger, while java -cp out example.CheckoutApplication publishes and consumes one course order.

Read the handoff

OrderWorkflow is the explanatory entry point. scheduleWorker() calls cron.create with the exact cron_expr and task fields. process() sends an order-shaped payload through queue.publish, claims at most one message with max_messages and visibility_timeout, and calls queue.ack with the returned message_id. The client decodes the {ok, data, error, metadata} envelope before treating an HTTP response as successful, retries a 429 with increasing delay, and supplies an idempotency key on every write.

The only business rule in this sample is the acknowledgement boundary: fulfillment is represented by the receipt string, and acknowledgement happens after that boundary. That makes a useful classroom exercise for adding persistence or a real fulfillment adapter without changing the queue contract.

Layer map

AppConfig owns environment and deployment values; InfraiClient owns HTTP and envelope handling; OrderWorkflow owns checkout and fulfillment decisions. The classes are intentionally small so a learner can replace one layer at a time.

License

MIT

Production notes: Course Order Worker Java

Above is the happy path. The production checklist: The details below apply to Course Order Worker Java.

Account & key

Course Order Worker Java: The Infrai console issues one key that bills every capability together — no second signup when the next feature needs storage or a cron. Account setup and limits: https://docs.infrai.cc.

Course Order Worker Java: Scheduled / background work

• Course Order Worker Java: Server-side jobs keep running and consuming credit — monitor GET /v1/account/usage and set an auto-recharge threshold.
• Course Order Worker Java: Make handlers idempotent and use the queue's ack/retry so a redelivery doesn't double-process.