Theme App Extensions ship blocks across many themes via the App Store, ideal for distributed apps with version control Local section schemas live in the theme repo, win for one-store custom builds with no review wait and full Liquid control Shopify Functions overlap on cart, checkout, discount, delivery logic and often beat both for backend rules Real schema snippets included plus a 5-question decision matrix that picks the right architecture in under a minute Honest tradeoffs: TAE has install ergonomics and reach, local sections have speed and freedom, Functions own backend logic I shipped two Shopify projects in the same week, one as a Theme App Extension and one as plain Liquid sections, and the architecture choice mattered more than any of the code inside. The wrong pick adds 4 weeks of app review for a feature that should have taken an afternoon. The other wrong pick locks a paying customer into a one-store snowflake they can never resell.…