Purpose of Heartbeat utility(Heartbeat.aspx) in Sitecore

You can access Heartbeat.aspx via /sitecore/service/heartbeat.aspx URL.

Heartbeat.aspx checks if all your SQL databases configured in your connectionStrings config are accessible.If they are accessible, it just render empty response.

If at least one of the databases is not accessible, it returns 500 Internal Error page and writes to the log file lines like:

5112 16:42:04 FATAL SINGLE MSG: Sitecore heartbeat:

Exception: System.Exception

Message: Database …………………… is not available

You can exclude some of the connection strings from being checked by Hearbeat using "Sitecore.Services.Heartbeat.ExcludeConnection" setting:

<setting 
  name="Sitecore.Services.Heartbeat.ExcludeConnection"
  value="some-connection-string-name-1|another-connection-string-name-2"/>

Happy learning :)