UPI: Anatomy of a Payment Transaction(timeseriesofindia.com)
timeseriesofindia.com
UPI: Anatomy of a Payment Transaction
https://timeseriesofindia.com/economy/reads/upi-architecture/
29 comments
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.
How is this different from Alipay/WeChat Pay in China? Handling transactions of this volume is an amazing technological feat, kudos to the team! However, I don't think this mobile QR code paying system is anything novel. Alipay rose to popularity much earlier (I can't recall exact when, but it was already super popular in ~2010, and definitely ubiquitous by 2015).
It’s a completely different backend model; as far as I know alipay works just like PayPal where transactions are fully “internal” - the buyer pays Ant Group and the seller cashes out at a later date.
UPI is a real inter-organization payment system more akin to credit card processing, where fund requests flow from the payer, through a payer processor, through a merchant processor, and finally to their end destination, and the actual reconciliation happens through a bank transfer system. It’s a much less centralized system.
UPI is a real inter-organization payment system more akin to credit card processing, where fund requests flow from the payer, through a payer processor, through a merchant processor, and finally to their end destination, and the actual reconciliation happens through a bank transfer system. It’s a much less centralized system.
UPI is more like a routing/reconciliation layer like VISA that can work across any bank/wallet, and that core is run by a non-profit government org. It doesn't take custody of the funds and doesn't centralize the information into a private corporation. The fee is also minimal and flat-rate with no profit incentive, instead of paying a percentage of the entire countries transaction volume to some private company. I would guess that adds up to a huge amount of money saved overall.
Much of the world doesn’t like having a single entity own and control the process end to end, it’s more efficient but there’s only one point of trust. Multiple institutions that have to check each other means you don’t have to trust a single entity with everything.
22B transactions a year mean an average of ~700 QPS for the NPCI switch. Of course the traffic is not uniform, it probably peaks at many times that number, but that still doesn't sound that bad - for comparison, a quick Google tells me Nasdaq TotalView ITCH feed peaks at 100k+ QPS at market open.
The right comparison for Nasdaq's order processing volume or messaging volume would be India's National Stock Exchange (NSE). It does more executed orders per day than nasdaq.
I worked on scaling UPI a few years ago. Real-time Payments is vastly more complex as it is much more distributed - each transaction involves the two banks holding funds, two end-user apps (and their banks), and the network (npci) – for the payment to complete end to end, multiple message exchanges need to happen between these parties while the user at both ends are waiting. So, if you measure the scale in messages/sec it would 10-25x higher.
Real-time payment rails that works 24/7 365 days a year from any bank to any bank (domestic, no exceptions) for free is truly a game-changer. Compare that to US payment rails which is slow and expensive. Apart from UPI, India has 3 more payment rails – NEFT (similar to ACH – batch settlement), IMPS (similar to UPI, instantaneous - but different user experience), RTGS (real-time, intermediated by the central bank RBI, but only for high-value transactions) – all are 24/7/365 and free. Then, there's credit card rails – apart from Visa and Mastercard, India also has RuPay which has much lower interchange rate.
I worked on scaling UPI a few years ago. Real-time Payments is vastly more complex as it is much more distributed - each transaction involves the two banks holding funds, two end-user apps (and their banks), and the network (npci) – for the payment to complete end to end, multiple message exchanges need to happen between these parties while the user at both ends are waiting. So, if you measure the scale in messages/sec it would 10-25x higher.
Real-time payment rails that works 24/7 365 days a year from any bank to any bank (domestic, no exceptions) for free is truly a game-changer. Compare that to US payment rails which is slow and expensive. Apart from UPI, India has 3 more payment rails – NEFT (similar to ACH – batch settlement), IMPS (similar to UPI, instantaneous - but different user experience), RTGS (real-time, intermediated by the central bank RBI, but only for high-value transactions) – all are 24/7/365 and free. Then, there's credit card rails – apart from Visa and Mastercard, India also has RuPay which has much lower interchange rate.
None of them are free, most banks now charge nominally (look at NEFT and IMPS charges). UPI itself is paid off by taxpayers.
Also RTGS is the only ISO 20022 complaint payment rail (back when it wasn't globally very common) - something that needs to be appreciated more.
People need to realise what NPCI offers is vastly different from what RBI offers. In my opinion what NPCI is offering will end up negatively impacting the general population in the long run.
Also RTGS is the only ISO 20022 complaint payment rail (back when it wasn't globally very common) - something that needs to be appreciated more.
People need to realise what NPCI offers is vastly different from what RBI offers. In my opinion what NPCI is offering will end up negatively impacting the general population in the long run.
Just for my curiosity, why do you think "what NPCI is offering will end up negatively impacting the general population in the long run."
22B in the month of June 2026, so 264B extrapolated annually.
Yep. Here's the accurate Month-to-date stats published daily by the network operator NPCI https://x.com/NPCI_NPCI. If you want official stats across all banks, across all payment rails, look at the central bank (RBI)'s website.
They put out a lot of useful stats here https://www.rbi.org.in/Scripts/Statistics.aspx
Daily payment settlement stats here: https://rbidocs.rbi.org.in/rdocs/content/docs/PSDDP04062020....
They put out a lot of useful stats here https://www.rbi.org.in/Scripts/Statistics.aspx
Daily payment settlement stats here: https://rbidocs.rbi.org.in/rdocs/content/docs/PSDDP04062020....
~8.8K TPS on average
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A great lesson for system design job interviews - if this is a popular payment system in a country with 1.5 billion people, your theoretical system you're designing for a small company cargo culting Google interviews will not likely support millions or even tens of thousands of average TPS.
Well, they are money-moving transactions which means each person only does them a few times per day. If your system's transactions are more like showing the weather on the home screen, it's plausible you could have orders of magnitude more traffic than a payment system.
Centralized, kyced, private money transaction network. Is this something good?
That's how government money works. This is the best possible system for handling government money. If you want an alternative you could buy some bitcoin with it.
way better than privately owned banks doing the same while extracting profits from users. better than todays crypto with terrible ux where its easy to lose all your money. more practical than cash (but that should still be an option).
worse than a system thats convenient and decentralized and anonymous at the same time, but we dont have one yet. maybe in 5 years when ethereum figures out native account abstraction, seamless scaling and monero level privacy.
worse than a system thats convenient and decentralized and anonymous at the same time, but we dont have one yet. maybe in 5 years when ethereum figures out native account abstraction, seamless scaling and monero level privacy.
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.
Yes it is. It's not trying to be new money, it's your money that already works.
I have heard nothing but good about it, from my Indian friends. They rave about it.
Yes, it is peak developed world financial infrastructure, ran as a utility under government direction.
How is it KYCd yet also private?
It's the intention and use case. The government want to reduce the fund leakages and reduce corruption, directly transfer the money to citizens, reduce transaction costs. Hence it works.
The government does not track all the transactions. You need a police FIR, to review these transactions.
In short, Indian government does not track or they don't have the scaling to track. But they can do it, if there is any criminal complaint.
The government does not track all the transactions. You need a police FIR, to review these transactions.
In short, Indian government does not track or they don't have the scaling to track. But they can do it, if there is any criminal complaint.
> In short, Indian government does not track or they don't have the scaling to track
This is completely wrong.
Not only can the Indian govt track each these transactions, it's actually written into law via the 'anti money laundering' bill (PMLA) and the income tax act. For a very high level overview, see https://www.bankbazaar.com/tax/tax-on-upi-transactions.html
From the article
'Can the Income Tax Department Track Your UPI Transactions?
Yes. With the integration of PAN, Aadhaar, and Know Your Customer (KYC) via all banking and fintech channels, all your UPI transactions can be tracked. If you think your small-value digital transfers won't be traced, you are mistaken. UPI payments are directly linked to your bank account, and bank records can be obtained by tax officers through scrutiny or reassessment.'
Specifically, no complaint or warrants are needed to enable access to UPI transaction records.
This is completely wrong.
Not only can the Indian govt track each these transactions, it's actually written into law via the 'anti money laundering' bill (PMLA) and the income tax act. For a very high level overview, see https://www.bankbazaar.com/tax/tax-on-upi-transactions.html
From the article
'Can the Income Tax Department Track Your UPI Transactions?
Yes. With the integration of PAN, Aadhaar, and Know Your Customer (KYC) via all banking and fintech channels, all your UPI transactions can be tracked. If you think your small-value digital transfers won't be traced, you are mistaken. UPI payments are directly linked to your bank account, and bank records can be obtained by tax officers through scrutiny or reassessment.'
Specifically, no complaint or warrants are needed to enable access to UPI transaction records.
Yeah globemaster99's point seems very naive.
> In short, Indian government does not track or they don't have the scaling to track
This is completely wrong.
Not only can the Indian govt track each these transactions, it's actually written into law via the 'anti money laundering' bill (PMLA) and the income tax act. For a very high level overview, see https://www.bankbazaar.com/tax/tax-on-upi-transactions.html
From the article
'Can the Income Tax Department Track Your UPI Transactions?
Yes. With the integration of PAN, Aadhaar, and Know Your Customer (KYC) via all banking and fintech channels, all your UPI transactions can be tracked. If you think your small-value digital transfers won't be traced, you are mistaken. UPI payments are directly linked to your bank account, and bank records can be obtained by tax officers through scrutiny or reassessment.'
Specifically, no complaint or warrants are needed to enable access to UPI transaction records.
This is completely wrong.
Not only can the Indian govt track each these transactions, it's actually written into law via the 'anti money laundering' bill (PMLA) and the income tax act. For a very high level overview, see https://www.bankbazaar.com/tax/tax-on-upi-transactions.html
From the article
'Can the Income Tax Department Track Your UPI Transactions?
Yes. With the integration of PAN, Aadhaar, and Know Your Customer (KYC) via all banking and fintech channels, all your UPI transactions can be tracked. If you think your small-value digital transfers won't be traced, you are mistaken. UPI payments are directly linked to your bank account, and bank records can be obtained by tax officers through scrutiny or reassessment.'
Specifically, no complaint or warrants are needed to enable access to UPI transaction records.
Maybe for some but likely not all
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