> synchronising 'cron.php' execution using .lock files.
A lock file, like a lock of a door, prevent others entering when one is inside! In this case it should serve only as an additional safety measuere. If it comes to action, you should inquire why.
BTW, the lock file resides in the file system of a sever, will fail if you rotate the cronjob.
Hardware and performance
Load-balanced web servers and cron.php
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