Turning your "app without code" (ex. inside) to traditional stack. How did YOU do it successfully?

Lately, I've been trying to post different topics here to engage users and get the creative juices flowing for myself and everyone else. Today, I'm asking about situations in which your simple, single-function or minimalist websites that you've built without code grew to require a traditional front-end/back-end architecture.

As an example of the above, picture an app built entirely using Zapier integrations. I'm going to make up something silly here, so bare with me:

Say you wanted to make affiliate money off of a simple website that recommends a coffee machine to coffee lovers based on their need and budget. Using the following flow, you could easily do this with Zapier integrations and NEVER require custom code, user logins, page routing, a back-end database, etc.

1. Typeform - User fills out a premade survey/form so we can collect email and learn about their coffee needs (do they prefer coffee pods/k-cups/ground beans/ espresso? do they want to brew single cup or enough for a whole family?, what is their budget?, etc.)
2. Google Sheets - receive and log all user responses and contact info from Typeform. In another Google Sheet, manually map all survey/form responses to a recommended coffee machine from Amazon that makes sense.
3. Mailchimp - Send email with nice template to user, using their email address and other contact information logged in our Google Sheets spreadsheet, and include in the email the coffee machine we recommend. This link will be an affiliate link and you'll make % off the sale. EASY!
4. Automation - If you're feeling fancy, you can use Google Scripts and other things within Zapier to automatically send the coffee machine recommendation email without having to do it manually.

Of course, once you need to implement user logins, manage users, do anything custom, display a growing or changing set of data, you'll need a database and other technology that a full Zapier-integration setup like the example above just won't be able to handle.

Were you ever in this situation? What did you do, and what do you recommend to people like me who have been relying on these integrations as a nervous response to diving into custom code solutions?