Thank you for these explanations and the node-resque package.
Yuval Steinberg

You can run more than one scheduler process at a time. They have internal tools (using redis) to allow for failover should one crash. Since Redis is single-threaded anyway, only one connection can do an operation at a time. Having more than one scheduler would increase your availability, but not necessarily your throughput. Yes, you could probably get more speed out of the system (as the schedulers do spend time parsing JSON and what not), but I’ve personally never seen the scheduler be a bottleneck.