3 ms·

"absolute consistency isn't a hard requirement for banks": see above. Yes it is. This one gave me a laugh. Thanks for pointing it out. Let me see.... Your bus

"absolute consistency isn't a hard requirement for banks": see above. Yes it is. This one gave me a laugh. Thanks for pointing it out. Let me see.... Your business does nothing but manage money. You don't need absolute confidence over where that money is at any given point of time? Right..... In fact accounting systems (and by extension ERP systems) are about the LAST place you'd want to use anything other than a relational database system/

einhverfr 15y ago
Re-reading the article I see what the author is saying, namely that some lag between the ATM network and the bank's accounting system is permissible. However, you still need to have a single point of truth that is absolutely consistent. If you don't, the bank's accountants (and probably federal regulators too!) will be rather unhappy! So the author takes a reasonable observation and twists it beyond recognition......
bwarp 15y ago
Most banks use an eventually consistent message oriented architecture, not a transactional one. At a low level banks use both absolute consistency (for physical transaction stores) and eventual consistency (for logical transaction implementations). The logical transaction implementation abstracts inter-bank and physical payment messaging. It would be impossible to have absolute consistency in the logical transaction layer as transaction scopes would have to be open (i.e. locked) for days at a time in some cases. That simply doesn't scale. Ultimately banks have millions if not billions of pounds floating around not in traditional transactional stores all the time.
- einhverfr 15y ago
  I agree that ATM's are a bad solution to this. The issue there though is loose coupling of third party financial networks though compared to a general need for consistency in terms of one's own financial needs. But loose coupling between third party payment networks (say debit card purchases over Cirrus) and the bank is not really the same problem as using Cassandra at Facebook.

einhverfr 15y ago

Re-reading the article I see what the author is saying, namely that some lag between the ATM network and the bank's accounting system is permissible. However, you still need to have a single point of truth that is absolutely consistent. If you don't, the bank's accountants (and probably federal regulators too!) will be rather unhappy! So the author takes a reasonable observation and twists it beyond recognition......

bwarp 15y ago

Most banks use an eventually consistent message oriented architecture, not a transactional one. At a low level banks use both absolute consistency (for physical transaction stores) and eventual consistency (for logical transaction implementations). The logical transaction implementation abstracts inter-bank and physical payment messaging. It would be impossible to have absolute consistency in the logical transaction layer as transaction scopes would have to be open (i.e. locked) for days at a time in some cases. That simply doesn't scale. Ultimately banks have millions if not billions of pounds floating around not in traditional transactional stores all the time.

einhverfr 15y ago
I agree that ATM's are a bad solution to this. The issue there though is loose coupling of third party financial networks though compared to a general need for consistency in terms of one's own financial needs. But loose coupling between third party payment networks (say debit card purchases over Cirrus) and the bank is not really the same problem as using Cassandra at Facebook.