The framing of "engines" implies they're separable, but in practice the sequencing decision is actually a positioning decision — which engine you scale first signals what kind of company you're building and shapes which customers you attract, which affects whether you can switch engines later.

Mostly agree, but the trap is when companies scale one engine so hard they never build the others — then when CAC spikes or the algorithm changes, they're exposed. At Shopify we think about these as complementary systems, not a ladder you climb one rung at a time.