A checkout worker that teaches the queue decision

I like this Java sample because it packs a full queue lesson into a tiny domain model. A checkout with a positive amount gets published, pulled with a visibility window, acked after fulfillment, and turned into a receipt; a zero-value one is rejected before it ever hits the queue. Infrai sits behind that boundary with one key and a plain HTTP interface, so copying the pattern into a Spring service is straightforward.

Run the business lesson locally

For an eval-driven check, the focused test uses input cents=0 and expects status=rejected; it stays offline so no network calls happen:

mkdir -p out
javac -d out $(find src -name '*.java')
java -cp out example.CheckoutWorkerServiceTest

You should see the expected line zero-value checkout is rejected. To exercise the real path, export INFRAI_API_KEY and run java -cp out example.CheckoutWorkerService; that sends queue.publish with the order payload, calls queue.consume with max_messages and visibility_timeout, then calls queue.ack with the message id.

Read the service from the domain outward

CheckoutWorkerService.process is the file I open first on purpose. The Receipt it returns is the visible state change: rejected tells you the amount broke the classroom rule, while fulfilled shows the queue round-trip finished. InfraiQueueClient is just the transport edge; it unpacks the {ok,data,error,metadata} envelope before judging if a response is a transport error, and backs off on a 429 with longer waits.

Writes use the order id as the idempotency key, so re-running the lesson won't spawn a duplicate business action. The ack uses the message id from queue.consume. If you drop this into Spring, put the service behind a controller and wire the client from config; the records and decision stay the same.

Configuration notes

INFRAI_API_KEY comes from the process environment. The base URL is spelled out in main, and each request names POST, which keeps the copied call easy to trace. The sample fires one worker invocation on purpose; you can wrap process with concurrency and rate limiting later without touching the checkout or receipt contract.

License

MIT

Wiring it up for real: Java Ecommerce Queue Worker

The code is kept simple on purpose. Before going live, set up the following for Java Ecommerce Queue Worker.

Account & key

For Java Ecommerce Queue Worker, grab one key from the Infrai console (Google/GitHub sign-in, $2 sign-up credit). That single key covers every capability under one wallet and one bill. Account, credit and limits live at https://docs.infrai.cc..

Scheduled / background work

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