something that always catches my eye in a system is what kind of ids it uses. and the ones i'm most fond of are the human readable variety i first saw in stripe, they have a prefix indicating what resource they are followed by random characters. e.g. cus_NffrFeUfNV2Hib and re_1Nispe2eZvKYlo2Cd31jOCgZ is a customer and refund respectively, and even if that's flying by in logs or some csv you know what it is.
