5 ms·

Do you know that, or is it your conjecture? There are a lot of other possible reasons to use $500 as a limit. For example, preventing people from structuring wi

Do you know that, or is it your conjecture? There are a lot of other possible reasons to use $500 as a limit. For example, preventing people from structuring withdrawals at the ATM, preventing an accident from producing too much cash, limiting the frequency with which ATMs need to be serviced, and limiting the downside of unauthorized withdrawals. It is true in some sense that the banking system is eventually consistent, because commands can be issued asynchronously. For example, you can issue a check, and expect it to be drawn in the future. However, that does not necessarily apply to the ledger itself, and given what I understand about banking technology, I'm somewhat surprised if it is truly as you describe. If it is indeed a conjecture of yours, I urge you to make it more clear in your comments when you are speculating and when you are speaking with authority.

deleted 9y ago
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PeterisP 9y ago
It's worth noting that in general there's no "the banking system" (unless we're talking about particular single systems e.g. Fedwire), there's a mismash of many different, highly diverse systems used by different organizations having quite opposite properties - for example, in the context of the comment above, I happened to participate in a cards system migration some 15 (?) years ago where the old system did have the eventual consistency issue described above (mostly mitigated by limits, there were just a couple times where double-spending happened), and the new system ensured strong consistency. So it can be one way, and can be the other.
jedberg 9y ago
I know that. I've talked with people who work on banking systems who have confirmed it. It's true there are other reasons for the limits, such as the ones you listed, but if you are with say Bank of America, your limit and my limit can be different. The more credit history you've built up with the bank, the higher the limit will be. This is mostly because they trust you more and therefore consider the risk for defrauding smaller.
- sambe 9y ago
  It takes a fraction of a second to send the withdrawal to the main office - how would a scam based on this really work? A second card with another person at a different ATM? Even then, you'd think you could serialise per-account without affecting throughput at all.
  - spdionis 9y ago
    > It takes a fraction of a second 99.999% of the time? It's impossible to guarantee that 100% of the time.
    - sambe 9y ago
      And it would still be acceptable to wait 0.001% of the time, would it not? Or degrade to limit mode in that situation?
  - Too 9y ago
    I'm not sure but I've seen Visa terminals that behave as if they enter some kind of offline mode when their ancient GPRS connection in the middle of the woods time out. In this mode you can only do smaller purchases and they are then later sent to the bank once the store gets a connection. This is for Visa debit btw, not credit.
    - sambe 9y ago
      Sure, a fail-safe mode makes complete sense. I'm just doubtful that there's a need to be in this mode 100% of the time.
  - Lanzaa 9y ago
    Here is a news article from 2013 about such a scam: http://www.nytimes.com/2013/05/10/nyregion/eight-charged-in-45-million-global-cyber-bank-thefts.html http://www.nytimes.com/2013/05/10/nyregion/eight-charged-in-...
    - 9y ago

deleted 9y ago

[deleted]

PeterisP 9y ago

It's worth noting that in general there's no "the banking system" (unless we're talking about particular single systems e.g. Fedwire), there's a mismash of many different, highly diverse systems used by different organizations having quite opposite properties - for example, in the context of the comment above, I happened to participate in a cards system migration some 15 (?) years ago where the old system did have the eventual consistency issue described above (mostly mitigated by limits, there were just a couple times where double-spending happened), and the new system ensured strong consistency. So it can be one way, and can be the other.

jedberg 9y ago

I know that. I've talked with people who work on banking systems who have confirmed it. It's true there are other reasons for the limits, such as the ones you listed, but if you are with say Bank of America, your limit and my limit can be different. The more credit history you've built up with the bank, the higher the limit will be. This is mostly because they trust you more and therefore consider the risk for defrauding smaller.

sambe 9y ago
It takes a fraction of a second to send the withdrawal to the main office - how would a scam based on this really work? A second card with another person at a different ATM? Even then, you'd think you could serialise per-account without affecting throughput at all.
- spdionis 9y ago
  > It takes a fraction of a second 99.999% of the time? It's impossible to guarantee that 100% of the time.
  - sambe 9y ago
    And it would still be acceptable to wait 0.001% of the time, would it not? Or degrade to limit mode in that situation?
- Too 9y ago
  I'm not sure but I've seen Visa terminals that behave as if they enter some kind of offline mode when their ancient GPRS connection in the middle of the woods time out. In this mode you can only do smaller purchases and they are then later sent to the bank once the store gets a connection. This is for Visa debit btw, not credit.
  - sambe 9y ago
    Sure, a fail-safe mode makes complete sense. I'm just doubtful that there's a need to be in this mode 100% of the time.
- Lanzaa 9y ago
  Here is a news article from 2013 about such a scam: http://www.nytimes.com/2013/05/10/nyregion/eight-charged-in-45-million-global-cyber-bank-thefts.html http://www.nytimes.com/2013/05/10/nyregion/eight-charged-in-...
  - 9y ago