I think the doc has contradictory info on whether a recent version of moodle can have a cron job in each node (asuming same app instance and one database) or only a cron job in one node:
For 2.7 cron job: NO
"If both your servers are web servers, and they jointly serve one Moodle instance (in some sort of a cluster), then only one server should run the Moodle cron job"
"Clusters with multiple identical application nodes are supported, you can run cron on all of them"
If using a version prior 2.7, one app instance, one DB, can I config a cron job in at least two nodes (for High Availability)?