Real time or close to real time with MySQL or MSSQL
My opinion is that polling in your case (10 seconds is OK to me) is better than the trigger solution. The trigger is closely coupled with your transaction, and can cause lots of un-expected issues that are hard to trouble-shoot. Personally, I have never used trigger to call external application (what if the application fails, long to start, stuck? )

A better (but more difficult solution) can be using service broker to engage with external application.