Judging the visible output as a metric for how many developers a company needs is very naive.

Think about the teams that don't directly interact with the outside like infrastructure, business intelligence, hiring (onboarding tools), internal tooling, all the work they do on Ruby (https://shopify.engineering/shopify-ruby-at-scale-research-i...).

Shopify probably employs many devs whose job is likely to pretty much operate as consultants for some of their larger customers.