You'll get a Shopify billing prompt. If you don't subscribe, your store drops back to the free plan — 1,000 recommendation views a month. Your products and orders are unchanged.
Is there a usage limit?
The free plan includes 1,000 recommendation views a month. Starter removes that limit for $19/month — unlimited views.
Can I cancel?
Yes — cancel directly in your Shopify admin under Apps. Blocks are removed immediately, no residue. Your store simply moves back to the free plan.