This line is tricky for this issue.

Remove all informations about previous enqueued job times. 
I am doing this for keeping Redis memory in bounds, but you can very easily rewrite this line to:
```conn.zremrangebyscore("#{cron_job_key}:run", 0, "(#{now - 1.day}")```

then it will clear all older enqueued times than yesterday.

So answer for you:

machine with time in most future will allways do adding job to queue
all machines with older time will try to add it, but in sorted set will be already this time stored so no other job will be added.

We can say that 1.day should be option called `time_treshold = 1.day` or whatewer user needs

What do you think about it?