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Comment by sdkmvx | Hacker News Reader

I just want to add that this is obviously true because ACID can be implemented on the filesystem, which is not ACID. So to create a reliable transaction processing system on MongoDB (or any non-ACID system), you would need to build ACID on top of it. And if you're interested in Bitcoins and not database design, that's probably not the right way to go.

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And if you build ACID on top of mongodb, then you lose the benefits of NoSQL. Not to mention the immense difficulty of building ACID into your business logic...

It makes sense to use mongodb for commenting system where nobody cares if you lose a comment or certain comments are written before others.

But no competent architect would use mongodb for financial/currency transactions.

If coinbase did use mongodb, it will be inevitable they will have transactional issues. The more popular coinbase gets, the more transactions they process, the more issues they'll have. I don't envy the poor souls that have to track down these kinds of issues...

Well, NoSQL doesn't simply mean "not ACID". There's also other stuff like documents instead of tables and native support for JSON.

On some of them. I have come to call anything that stores data in a non-SQL way NoSQL. Accurate? Probably not, but it sure does seem to bring in those other ones that everyone calls NoSQL for some reason (Redis for example).

FYI: TokuMX builds ACID underneath MongoDB. They ripped out Mongo's storage engine and replaced it with their own. It seems to be faster and it supports ACID transactions.

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