The National Payments Corporation of India’s root cause analysis for the April 12 UPI outage report said that a heavy load of transaction success requests from merchants and banks hit the system than was permitted, causing the platform to face downtime.
Moneycontrol has accessed the report that NPCI has sent to UPI entity partners. NPCI runs UPI, the country’s most popular digital payments system.
“The issue was identified to be caused by the flooding of 'Check transaction' AΡΙ. Further, it was observed that a few PSP Banks were also sending requests for 'Check transactions' even for older transactions multiple times,” the NPCI report said.
UPI faced four outages in the last three weeks, causing major inconvenience to millions of people.
Banks check whether a transaction was successful or not when they do not get a response from the customer’s beneficiary bank. This could be because the beneficiary bank’s server might have been down and it could not respond to a transaction success check request from a PSP bank.
A payment service provider (PSP) bank is the UPI app’s banking partner that connects them with the NPCI system. If the PSP bank does not get a response, it tends to check for the transaction success status repeatedly at a fixed time interval so that it can decide whether it should start processing more payments.
According to NPCI, the PSP banks also did not wait for the response from UPI system and were repeatedly flooding the UPI system with 'Check transaction' requests leading to further congestion in the system, and prolonged downtime for the platform.
As per NPCI operating circulars, the "Check Transaction" API call needs to be used only once in the interval of 90 seconds.
The RCA report said that NPCI advised the PSP bank to immediately stop the "Check Transaction" feature at 4 pm. It also deployed a temporary solution at 4:15 pm to mitigate the cross-site flooding and processing of 'Check Transaction' API's.
NPCI said that it will monitor the system for any other anomalies.
“It will be reiterated to the PSP Banks, the NPCI guidelines regarding the use of 'Check Transaction Request' APIs. The raw data files are available to PSP Banks and Acquiring Banks with the final status of the transactions (source of truth) every 2 hours. Banks and their partners are advised to use these for confirming transaction status instead of flooding the system,” the report said.
“The report does not say how this started. Banks check transactions when a lot of transactions fail in the system. It does not specify the origin of the problem,” said a banker, who has seen the report.
NPCI observed a reduction in UPI success rates on 12th April 2025, the report said. The success rate degraded to around 50% for about 2 hours and to around 80% for the next 3 hours between 11.40 am to 4.40 pm, it added. The success rate returned to normal at 4.40 pm on 12th April 2025, it noted.
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