User authentication problems were badly affecting several customer-facing applications, causing significant delays and downtimes. There was no reasonable explanation why this was happening. ESI was instrumental in pinpointing the problem.
A load test was set up to resend a thousand requests of the previous day against the authentication system – at a rate 40 times faster than normal. The local test results did not show any evidence that the problem resided on that system, suggesting that the issue could be elsewhere. New tests were conducted, but this time ESI was used to monitor the load test. Using ESI dashboards, it was clear that the failure occurred when a specific authentication API request was sent a number of times. Moreover, when this happened, it was found that other API requests were affected too. ESI guided the IT team to the root cause of the issue, a problem with a resource pool on the authentication system.