4 ms·

Data consistency is overrated if your business is ok with that. Many businessed are not ok with that. Example: airline, booking process.

fbdab103 4y ago
Airlines are notorious for over-booking available seats and dealing with the fallout.
- StreamBright 4y ago
  Which is done purposefully and not by data in-consistency at all.
  - macintux 4y ago
    I would wager, in complete ignorance of the real implementation, that the knowledge that they can overbook means that they can relax some of their requirements. If two servers can’t talk to each other to coordinate for a while, they could still each sell tickets.
  - esailija 4y ago
    No, it's because of CAP forces to make a compromise. If there was a way to be available and consistent there would not be overbooking. But they chose availability because losing sales is worse than dealing with overbooking. Exactly same with Amazon, they will not bother checking that the product is actually available because then you will miss the sale when the warehouse service is down or slow, which it would be all the time because it has to be a single place of failure. Its better to refund orders for non existent items than to miss sales. Consistency requires single source of truth which implies single place of failure. There is tremendous cost to it, it's not done for no reason like you say.
    - StreamBright 4y ago
      > there would not be overbooking. This is not the case at all. Airlines operate on the principle that a certain percentage of customers are no show. They would like to fly the planes fully booked so they allow some overbooking and they are controlling how much it gets overbooked. If it was up to CAP there would be 200% overbooking for certain flights and the airline would go bust within a year.
taeric 4y ago
Bad examples. Airlines are notorious for having incoherent booking policies. Over selling flights and such.
- crazygringo 4y ago
  Overbooking is intentional policy. It has nothing to do with data consistency. To the contrary, consistency is extremely important so that they overbook by exactly the right amount, to compensate for the statistically expected no-shows.
  - taeric 4y ago
    It is a form of coherence for the system, though. And in the spirit of the same ideas. That is, it is an intentional policy for databases, too. And there is no "exactly right amount" that makes it work. They keep options for forcing people off flights if they planned it wrong. Is also why they don't let gate agents over sell a flight. They keep a stronger consistency on that, for this exact reason. Over selling would fit in what someone else called external consistency.
jhallenworld 4y ago
How about I order something, but the inventory was off, so I never get my item. This is how you get unhappy customers. You could have buffer inventory to help with your bad system, but then you are tying up money in inventory..

fbdab103 4y ago

Airlines are notorious for over-booking available seats and dealing with the fallout.

StreamBright 4y ago
Which is done purposefully and not by data in-consistency at all.
- macintux 4y ago
  I would wager, in complete ignorance of the real implementation, that the knowledge that they can overbook means that they can relax some of their requirements. If two servers can’t talk to each other to coordinate for a while, they could still each sell tickets.
- esailija 4y ago
  No, it's because of CAP forces to make a compromise. If there was a way to be available and consistent there would not be overbooking. But they chose availability because losing sales is worse than dealing with overbooking. Exactly same with Amazon, they will not bother checking that the product is actually available because then you will miss the sale when the warehouse service is down or slow, which it would be all the time because it has to be a single place of failure. Its better to refund orders for non existent items than to miss sales. Consistency requires single source of truth which implies single place of failure. There is tremendous cost to it, it's not done for no reason like you say.
  - StreamBright 4y ago
    > there would not be overbooking. This is not the case at all. Airlines operate on the principle that a certain percentage of customers are no show. They would like to fly the planes fully booked so they allow some overbooking and they are controlling how much it gets overbooked. If it was up to CAP there would be 200% overbooking for certain flights and the airline would go bust within a year.

taeric 4y ago

Bad examples. Airlines are notorious for having incoherent booking policies. Over selling flights and such.

crazygringo 4y ago
Overbooking is intentional policy. It has nothing to do with data consistency. To the contrary, consistency is extremely important so that they overbook by exactly the right amount, to compensate for the statistically expected no-shows.
- taeric 4y ago
  It is a form of coherence for the system, though. And in the spirit of the same ideas. That is, it is an intentional policy for databases, too. And there is no "exactly right amount" that makes it work. They keep options for forcing people off flights if they planned it wrong. Is also why they don't let gate agents over sell a flight. They keep a stronger consistency on that, for this exact reason. Over selling would fit in what someone else called external consistency.

jhallenworld 4y ago

How about I order something, but the inventory was off, so I never get my item. This is how you get unhappy customers. You could have buffer inventory to help with your bad system, but then you are tying up money in inventory..