In October 2025, we rehearsed a surge in first-notification intake using synthetic messages and an agreed traffic pattern. The service could acknowledge ordinary traffic, but a burst of 1,800 submissions per minute caused acknowledgement latency to climb and duplicate retry messages to enter the processing queue. The exercise concerned technical intake. It did not represent an actual catastrophe or the insurer's ability to assess and settle the resulting claims.
Infrastructure colleagues proposed increasing the front-end capacity alone. Claims operations were concerned that rapid acknowledgements could be presented as completed claim handling while work accumulated behind them. I supported a queueing and duplicate-recognition change with separate measures for acknowledgement and downstream processing. The decision required more operating visibility and a defined way to show pending work, rather than a single green status for the entire service.
Eight weeks of work cost JPY94 million. In the repeated thirty-minute rehearsal at 1,800 submissions per minute, the 95th-percentile acknowledgement time fell from eighteen to six seconds. Of 54,000 synthetic submissions, 2,160 were deliberate retries. The revised service associated those retries with their original intake records, leaving 51,840 distinct records for downstream work. We retained the distinction between submissions and distinct records in the report.
The queue still took seventy-four minutes after the burst ended to finish the defined downstream technical processing. That elapsed time was not a claim-assessment or settlement measure. I included it because faster acknowledgement alone could obscure an important continuing workload. Operating colleagues retained responsibility for the staffing and decisions needed beyond the technical intake boundary.
The result improved the tested handling of a specified burst and made the remaining work easier to see. It did not establish readiness for every catastrophe scenario or a service promise to policyholders. In a future rehearsal I would agree the language of the operating status report before choosing the technical benchmark, so that a useful acknowledgement result cannot be mistaken for completion of the customer's wider claim.