[hinkley]

Before 'eventual consistency' was coined as a phrase, there was an old, powerful and deeply unsexy form of eventual consistency called "batch processing".

For small batches you do an interval at a convenient time, such as a time of day where the hardware is undersubscribed for some other task. As the batches grow then you have an online system that continues to work until you get rather far down the list of consequences in queuing theory. Once you get 24 hours and 1 minute of tasks per day you never catch up (it never ceases to amaze me how often I can find someone who will fight me on this point), and you must be aware that substantially before that breaking point, you can experience rather long average queuing delays.

But if your workload is spiky, you can smear 250 minutes of peak traffic out over 6-18 hours with no problems at all. You need a safe place to stash the queue and a little sophistication around recovering from failures/upgrades. Those aren't necessarily Simple tools, but if that's the most complex part of your system you're doing pretty okay.