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You’re totally right. However while this is useful to bootstrap a new technology rollout, 10 years on its just technical debt. The amount of tech debt in the

You’re totally right. However while this is useful to bootstrap a new technology rollout, 10 years on its just technical debt. The amount of tech debt in the system behind credit cards is crazy, because originally charges where phoned in to the card issuer manually, and everything from then on - magstripe, chip & PIN, online only transactions, etc, has all been built on top, and the leaky abstractions show through in daily difficulties with the card system for end users, like lack of real-time balance (in some cases), lack of transaction metadata, etc.

derefr 9y ago
On the other hand, the credit card system's backcompat does mean that you can still accept credit cards when the power's out. You just write down the number (or use an imprint machine) and let the customer go. And the semantics of credit mean that you can still make that charge even if an online transaction would have resulted in a decline—offline transactions are never declined, they just cause overdrafts.
- s73v3r_ 9y ago
  Yeah, but around here, most places just say the system is down and require cash.
- zbentley 9y ago
  I wonder if that resilience is worth the immense amount of infrastructure and engineering that is spent on maintenance of the technical debt. Does that maintenance drive up processing fees? I suspect it does, but not in any amount sufficient to explain the size of those fees.
- danpalmer 9y ago
  True! Although I think that's more of a byproduct, rather than something designed into the system at the moment, and I suspect we could do better with designing it. For example, I doubt many shops have those imprint machines any more. I also think the tech debt is holding us back a long way. For example, why can't I see itemised receipts in my card statement? Paper receipts are on their way out, email receipts aren't linked to anything or structured data, but being able to see that I've spent $120 on shipping with Amazon in the last 12 months, so a Prime subscription would make sense, would be a great sort of financial tool to have. That isn't possible in the card network at the moment.
  - Piskvorrr 9y ago
    They imprint "machines" are still issued - but all* of them are just tossed away into storage, and never ever used (Training users on those? Pointless).

derefr 9y ago

On the other hand, the credit card system's backcompat does mean that you can still accept credit cards when the power's out. You just write down the number (or use an imprint machine) and let the customer go. And the semantics of credit mean that you can still make that charge even if an online transaction would have resulted in a decline—offline transactions are never declined, they just cause overdrafts.

s73v3r_ 9y ago
Yeah, but around here, most places just say the system is down and require cash.
zbentley 9y ago
I wonder if that resilience is worth the immense amount of infrastructure and engineering that is spent on maintenance of the technical debt. Does that maintenance drive up processing fees? I suspect it does, but not in any amount sufficient to explain the size of those fees.
danpalmer 9y ago
True! Although I think that's more of a byproduct, rather than something designed into the system at the moment, and I suspect we could do better with designing it. For example, I doubt many shops have those imprint machines any more. I also think the tech debt is holding us back a long way. For example, why can't I see itemised receipts in my card statement? Paper receipts are on their way out, email receipts aren't linked to anything or structured data, but being able to see that I've spent $120 on shipping with Amazon in the last 12 months, so a Prime subscription would make sense, would be a great sort of financial tool to have. That isn't possible in the card network at the moment.
- Piskvorrr 9y ago
  They imprint "machines" are still issued - but all* of them are just tossed away into storage, and never ever used (Training users on those? Pointless).