There is one clean dishwasher and one dirty dishwasher. You take plates from the clean dishwasher, use them, and put them in the dirty dishwasher. Once the clean dishwasher is empty, the dirty dishwasher is run, and then becomes the clean dishwasher, and the empty one now becomes the dirty dishwasher.
There are analogous situations in system design as well.
There will always be some items that are left in the 'clean' dishwasher - eg. that lemon squeezer you only use once a month.
Also, with two dishwashers, thats a lot of cutlery/crockery in one or other dishwasher. Sometimes the cupboard is empty. Now every time you want an item, you need to check the cupboard and the dishwasher.
You might say, why have a cupboard, simply only store your plates in the dishwasher. But sometimes I have stuff that needs washing but I haven't yet used up all the clean plates... So I need somewhere to empty them out to.
every cupboard in your house is a dishwasher. The dishwashers are smart, and if they have been opened, they know there might now be something dirty in them, so they will wash overnight that night. It's wasteful of energy because you'll be washing 99 clean plates and one dirty plate, but I think it would lead to a good user experience.
For commercial customers, absolutely. I first came across services like this a long time ago in Hong Kong[1] but it's pretty widespread in mainland China, Taiwan, and parts of SEA[2] because local restaurants tend to be quite small. Sometimes you can tell because you'll get your dishes as sets in sealed plastic[3] wrappers.
1. https://www.ezwash.com.hk/en/services/
2. I've never personally seen it in Japan or South Korea, but I'm sure it exists.
3. https://countryandahalf.com/chinese-dining-etiquette/ (see the second pic in this article)
Instead of every cabinet being its own dishwasher, you could have a wall-mounted dishwasher that automatically distributes clean dishes back to the cabinets.
Maybe this will be my retired-and-bored passion project later in life.
Building on how I think I'd treat them is closer to a ringbuffer of workers. Would look a lot like the front/back idea in slow use, but I could easily see bursting through to where I have both running at once. And the destination of dishes out is still to the cabinets, for many other reasons.
Not that I'd ever do something like that.