100 trillion kobo = 100,000,000,000,000 kobo (10¹⁴)
A standard SQL BIGINT = 9,223,372,036,854,775,807 (~9.2 × 10¹⁸)
So 100 trillion kobo is nowhere near the BIGINT limit.
They were storing balances in kobos. 😆
I asked, "If a customer has 1 trillion, how will you represent it in the database?"
That becomes 100 trillion kobos.
Then comes the real question: How are you handling overflow?