Fintech/finance is a very big industry and there are a lot of sub-domains. A HFT system programmer thinks about how to colocate their prod machines in NYSE and use zero alloc techniques to ingest marketdata as fast as possible, while a crypto wallet app developer spend more time designing cool UI to attract users and working out all the L1/L2 quirks. And I'm sure they have very different answers to whether to use integers and how many digits to preserve