The hard parts of a Shopify app are rarely the features. They are the distribution choice, the
The public-versus-custom decision is made before any code exists and determines your review obligations, billing model and support burden.
Extensions are the modern surface — theme app extensions, checkout UI extensions and Functions replace the old pattern of injecting code into themes.
Shopify's own requirements checklist is a substantial part of the build, not a formality at the end.
Performance is a review consideration and a merchant retention issue, because an app that slows storefronts gets uninstalled regardless of its features.
A genuinely simple app with one clear function can be a few weeks.
The full guide has the formats, the deadlines and the worked examples.