[baconizer]

not sure why you're downvoted, the point is quite valid. I worked on both sides. They may seem similar from afar over the big picture but largely distinct in details and thereafter scaling tricks.

Trading on both buy and sell sides are highly structured data, and post trade requires high level of interpolation among data entities.

Payment processing data unit are somewhat unstructured / document based (payer/customer details, payment intent, plans, gateway infos..), but each payment object are quite isolated from each other. Post payment there are some interpolation if system is dealing with payouts account ledgers, but far from level of trading risk management (particularly derivatives).