Timer job

I get around 8000 requests per day on an average. Hence, there could be around 30,000 open/unattended requests at a given point of time. All requests at tagged with expiry date/timestamp. How to check and trigger the escalation for the open/unattended requests that have expired? The escalation triggering should be with minimum or no time lag.

If I create and schedule a batch job which runs every 5 mins to check and escalate the requests, then there would be time lag of 5 mins for some requets.