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by jaywalk 1463 days ago
Their system was basically designed the way you're saying, with a fallback to grab the data from the central location if it's missing locally. What you're asking for is the same system without a fallback, which doesn't make any sense.
2 comments
kevan 1463 days ago
It's counterintuitive but when you're dealing with distributed systems lots of things are: https://aws.amazon.com/builders-library/avoiding-fallback-in...
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bombcar 1463 days ago
Exactly - they had a fallback system that worked well enough for the testing to pass, but not well enough for the main system to operate on it.

Interestingly enough the Amazon example there is basically exactly what happened to Target.

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bombcar 1463 days ago
The fallback was the problem - design it without it, or with a manual window that pops up saying "ITEM NOT FOUND, QUERY TARGET ORACLE" or something, and the fault wouldn't have taken down the whole company.

If suddenly every cashier is being forced to hit OK on every item, people would hear about it immediately from the test rollout instead of when it hit everything (of course, assuming you have good methods for detecting things like this and don't just completely ignore associates' complaints).

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