The site periodically becomes unavailable with HTTP 500 error. All I could find from the logs so far is:
ModuleName iisnode
Notification EXECUTE_REQUEST_HANDLER
HttpStatus 500
HttpReason Internal Server Error
HttpSubStatus 1001
ErrorCode The system cannot find the file specified. (0x2)
Note that response time in this instance is around 38 seconds. I suspect this happens because IISNode process goes to sleep and the when it wakes up it fails on the first request after long time out. I created Azure WebJob that pings the site every 15 minutes to keep it alive and it seemed resolved the issue. I am just wondering if there's a better solution.