WhatsApp chose engineering cost first. It's a singular device only service, they do not retain any messages and a slew of other decisions. Look at their iOS c

WhatsApp chose engineering cost first. It's a singular device only service, they do not retain any messages and a slew of other decisions. Look at their iOS client for more examples of engineering cost first. A new client for an obscure phone costs about 1 engineer for WhatsApp too. Twitter is not an engineering cost first company.