How does Curve store card?

Can anyone please tell what technology does Curve use at the backend to store cards and what technology does Curve Send use to make transactions from Card to Card/Account?

It’s probably identical to how any random merchant like Amazon does it. Each time you use your Curve card in a store or online, Curve acts as a merchant and just takes the money from the credit card you currently have selected in the curve app. Curve Send is probably similar - just get money from one credit card and issue a refund to another credit card.

So your saying that Curve stores the Card just like how Amazon stores card information right? But how does card blocking or card settings works on Curve if it just stores the card information like Amazon.

And does Curve Send use any API to send money to card/account from card?

How does Curve Go back in time works?

When you use your Curve card, the store you are in sends to Curve “hey give me 10€ from this guy’s card”. then curve says “hold on let me check if there’s enough money”, then in the background it talks to your bank: “Hey I’m Curve, this guy just bought something for 10€ give me 10 €”. Then Curve gets the 10€ from your actual card, and then responds to the store you are in “all OK, here’s the 10€ you want”.

It’s basically two completely seperate card payments. And if you block your Curve card in the app, then all Curve does it just immediately respond with “get lost, this card is blocked” instead of talking to a real bank.

And GBIT (go back in time) is also pretty simple - it would be the same as if you went back to the store, returned whatever you bought for a refund, and then immediately, while at the till, buy the same item with another card. When you move a charge from card A to card B, Curve just tells card A “hey I’d like to refund the money to the customer”, and does a normal additional transaction on card B.

I want to know how they built this tech on the backend and did they built it in-house or are they using any existing technology( like API’s)?