India, April 4 -- The financial year has begun as somewhat of a mixed bag for India's unified payments interface, or UPI - and its scale means every transitional moment is amplified. The purging of inactive mobile numbers from UPI, is definitely a step towards safety. But the second outage in a week, this time late Wednesday night, something of a worry. Yet, as far as transitional moments go, we may be rushing towards another one.

An introduction (or re-introduction, for the justly pedantic readers) of MDR, or merchant discount rate, charges which will help banks and payment platforms earn a share from every UPI transaction. I mentioned scale earlier - and here are some numbers before I illustrate what this MDR transition may mean. UPI t...