Tag
The unanswerable-timeout thought experiment, the implementation with its three traps disarmed, why the property must compose down the whole call chain, and the cheaper natural-key alternatives.
The in_app_purchase integration done properly: the purchase stream from app start, pending states, completing purchases before Play auto-refunds, and the backend validation that makes revenue real.
One client per terminal, an explicit state machine, first-class timeouts and cancellation, idempotent references, verbatim receipts and the observability that keeps payment lanes boring.
Four families of payment errors, one correct reaction each: classification code, the recovery query that prevents double charges, dispute-winning logs and a test plan for the ugly paths.
Deploy payment middleware like any other workload: a production-shaped compose file, terminal networking options, log persistence for compliance and settlement-safe rollout pipelines.
The EftPeer operation lifecycle from a POS developer's seat: connect and login, purchase outcomes, reversal vs refund, recovery queries and the end-of-day settlement everyone forgets.
How to run Treibauf's pepperQik EFT middleware as a Windows service: installation, service accounts, crash recovery, firewall scoping and the operational checklist before go-live.
