How can have a RecurringJob firing in all servers at the same time. By default the job just run in one of the servers.
A RecurringJob is enqueued by a random(!) Hangfire server queue whenever the cron is triggered.
You simply need to either create one RecurringJob for each Hangfire server, or create one RecurringJob that enqueues a BackgroundJob for each Hangfire server. I would probably suggest the latter, enqueueing a new BackgroundJob for each Hangfire server.