UPI: Anatomy of a Payment Transaction • Hacker News Board

Re: UPI: Anatomy of a Payment Transaction

#121

Post by pixelatedindex » Sun, Jul 12, 2026, 5:58 PM UTC

fakedang wrote: post #31

pixelatedindex wrote: post #15

Earlier quoted context omitted.

It’s extremely good, at least in terms of user experience and how practical it is. Adoption is massive and at small chai shops it makes transactions a breeze, allowing businesses to serve more volume. The downside is making it incredibly frustrating for foreigners to pay using this as it’s tied to your government ID that your bank has authorized.

I mean it's not like foreigners are blocked from using cash at those stores. And if they prefer cards, it's not like the stores that used to accept them stopped accepting them.

Funny story… I was on a trip to Europe (Poland) using my US credit card that didn’t have tap to pay or chip and pin (I believe it was swipe only) and the store literally did not have a way to accept payment and I had no cash on hand.

They were nice enough and gave the pastry for free because they tried everything to charge the card but it didn’t work. They were embarrassed about the whole thing and were just like… please leave.

Re: UPI: Anatomy of a Payment Transaction

#122

Post by xk3 » Sun, Jul 12, 2026, 7:28 PM UTC

navigate8310 wrote: post #104

miki123211 wrote: post #78

Earlier quoted context omitted.

Systems that are based on one-time codes instead of permanent credentials are really under-appreciated in the anglosphere. Giving your credit card to your child / friend / spouse / subordinate, so that they can buy something with your money, is a lot more risky than giving them an OTP, valid for a single transaction, which you have to approve in your app anyway. Poland's Blik is based on 6-digit codes, which makes th…

Because those OTPs can be intercepted by any MITM unless you are using on-device 2FA generated by an app.

> intercepted by any MITM

Most things are... even SSH is Trust-on-First-Use. You can really only verify out of band. OTP is quite a bit better than CC or bank account numbers... assuming the OTP is only restricting use (and not giving access to view or modify other account information, etc)

Re: UPI: Anatomy of a Payment Transaction

#123

Post by malshe » Sun, Jul 12, 2026, 7:58 PM UTC

pixelatedindex wrote: post #15

jesuswasjew wrote: post #5

Centralized, kyced, private money transaction network. Is this something good?

It’s extremely good, at least in terms of user experience and how practical it is. Adoption is massive and at small chai shops it makes transactions a breeze, allowing businesses to serve more volume. The downside is making it incredibly frustrating for foreigners to pay using this as it’s tied to your government ID that your bank has authorized.

I was in India in December 2024 and visited three states. I experienced no problem in using my credit card. For smaller amounts I simply used cash. Altogether I spent less than Rs 1,000 in cash mostly for tea. In all other places a credit card was fine.

Re: UPI: Anatomy of a Payment Transaction

#124

Post by bspammer » Sun, Jul 12, 2026, 8:36 PM UTC

elendilm wrote: post #17

I have the utmost respect to people who makes UPI work. Made even the old people in the nation completely go digital for payments - a feat unparalleled in the world.

China is very similar, no one uses cash

Re: UPI: Anatomy of a Payment Transaction

#125

Post by inigyou » Sun, Jul 12, 2026, 9:24 PM UTC

hgoel wrote: post #114

inigyou wrote: post #95

Earlier quoted context omitted.

Do you have plans for when the government interprets your small payments as terrorism and seizes your bank account? I think every country goes through this and then goes back to cash, but at different rates.

Why would they interpret a system being used for the purpose it was designed for as terrorism? Using it for small purchases is one of the intended use cases, e.g. allowing street vendors to accept digital payments, incentivising them to have a bank account and reducing the risk of theft.

[flagged]

Re: UPI: Anatomy of a Payment Transaction

#126

Post by ksec » Mon, Jul 13, 2026, 7:23 AM UTC

HexDecOctBin wrote: post #119

ksec wrote: post #117

PIX from Brazil which is extremely similar to UPI. Are there any reason why we can't have a global UPI system? Open Source with each Government running their own instances.

UPI has been adopted by eight countries and a few dozen are in progress [1]. Additionally, UPI has started to integrate with other nation's similar system (Singapore's PayNow [2] for instance). [1] https://www.pib.gov.in/PressReleasePage.aspx?PRID=2224505&re... [2] https://www.nipl.com/how-it-works/frequently-asked-questions...

Oh nice so this is really happening!

Re: UPI: Anatomy of a Payment Transaction

#127

Post by brabel » Mon, Jul 13, 2026, 9:48 AM UTC

vickychijwani wrote: post #106

brabel wrote: post #90

Earlier quoted context omitted.

I think it was the same with PIX in Brazil, and Swish in Sweden, and probably many more precedents.

Don’t know about Swish but UPI heavily influenced Pix, from its open architecture, alias-based addressing, and QR code infrastructure

Oh I didn't know that... Swish is quite different so I would expect it to be a completely independent invention, and in any case I don't really know which is older.

Re: UPI: Anatomy of a Payment Transaction

#128

Post by porridgeraisin » Mon, Jul 13, 2026, 10:36 AM UTC

dyauspitr wrote: post #110

porridgeraisin wrote: post #80

Earlier quoted context omitted.

Yes this. Anytime a SaaS supports UPI Autopay, I'm 10-100x more likely to subscribe. For context: it's basically a recurring payment but you open the Autopay section in Google pay or whichever app and it shows you all your subscriptions right there (which is a major +), the transaction history, and cancellation happens in the UPI app itself I don't have to faff around in the SaaS and deal with potentially some dark p…

That’s absolutely huge. All your subscriptions in one place that you can just turn off from there directly. It’s one of my favorite things about payments going through the apple App Store.

Unlike the app store, there is no 30% fee. And also. No chargebacks, so it's simple for merchants as well.

Re: UPI: Anatomy of a Payment Transaction

#129

Post by tecoholic » Mon, Jul 13, 2026, 11:22 AM UTC

solarengineer wrote: post #120

tecoholic wrote: post #77

Earlier quoted context omitted.

Thanks for the additional info. But I want to clarify one thing - I didn’t say anything about cash being a better choice. Both the comments to my response are making it out to be a cash vs digital thing. I am not sure why. Next, NPCI is a PSU. So what? They are taking govt money to function aren’t they? The costs are borne by the banks which get allocations every budget to keep the system running. So whatever “profit…

If it is acknowledgement that you ( and others, I have spoken to various people on this topic) seek that UPI incurs costs, then here you go - I, a fellow tax-payer, acknowledge that the UPI must incur costs. I find it acceptable to allocate tax money for a system that we as a country can use as an alternative to the Visa and MasterCard duopoly. With UPI as it is today, there are no margins added and passed to the cus…

Hello everyone. I am really not sure what I was ranting about yesterday. I have some bones to pick with the system. The crux of it is - it’s not a technological miracle. It’s the government’s will that makes the system function. It’s good for what it does. But I was annoyed by the propaganda like manner people seem to talk about it in discussions.

I didn’t channel them properly and got into an argumentative fit. I apologise for wasting all your time.

Re: UPI: Anatomy of a Payment Transaction

#130

Post by fakedang » Mon, Jul 13, 2026, 12:29 PM UTC

pixelatedindex wrote: post #121

fakedang wrote: post #31

Earlier quoted context omitted.

I mean it's not like foreigners are blocked from using cash at those stores. And if they prefer cards, it's not like the stores that used to accept them stopped accepting them.

Funny story… I was on a trip to Europe (Poland) using my US credit card that didn’t have tap to pay or chip and pin (I believe it was swipe only) and the store literally did not have a way to accept payment and I had no cash on hand. They were nice enough and gave the pastry for free because they tried everything to charge the card but it didn’t work. They were embarrassed about the whole thing and were just like… pl…

I'm not sure whether this is fully correct - most card machines do have a way to accept swiping, but I think the store did not know of it (because no one uses it in Europe). Perhaps if you remember the provider, I could check it, but most machines still accept swiping, which is innocuously placed on the side of the machine.

That being said, the US is a dinosaur when it comes to payments.