> I ofc don’t know what I dont know, but super curious if anyone has insight into why such a complex system is required

Because it's much more efficient, which allows them to use simpler tech that doesn't need to scale as well.

You are also underestimated the throughput the system needs to handle. 2000 stores * 10 registers per store * 1000 scans per register per hour = 5000 scans per second.

I’m not sure the throughput is that high - scans take quiet a bit of time, I would doubt that a register scans an item every 3.6 seconds - don’t have data on this but would easily triple that estimate as an average (so in the hundreds)

Also , I get the simpler tech, but complexity breeds failure - if you have a hybrid on prem / cloud model, especially with only 250k skus, at that point doesn’t it make sense to keep that exclusively in the cloud.

It’s a system that scans a barcode and returns an item at its core - this is still well under the limits of using an off the shelf system like Redis behind an endpoint

"I would doubt that a register scans an item every 3.6 seconds"

Indeed, that sounds WAY too slow for me - traffic like this is bursty. Ever try to scan five of the same thing at some self check out registers? On some it's instantaneous (an awesome customer experience) on others there are one second or more delays (horrible customer experience).

Latency = friction and friction is the ultimate deal killer.

Walmart is the worst, it takes multiple seconds to even register that the scan worked.

Not being able to check out customers is a really bad customer experience. It's a double whammy of wasting their time and they don't even get what they needed so it's worth investing to make that less likely. Things are probably better now but when I worked at a Sears our network connection to HQ wasn't reliable enough to depend on completely for checkout operations.