The least painful approach is (and always has been) to write the entire (e-commerce) (web) app in Smalltalk, specifically Squeak (or several forks like Cuis, Pharo). I once wrote an entire webshop with Stripe payments in a single afternoon that had the sophistication of the Apple Store.

There is not one framework but several, some are mainly Smalltalk, some are more javascript wrappers or ported to javascript. I have omitted a lot of other 'Smalltalks in the browsers'. Another language would be LISP, like [9] in which HN itself is build. I'd love to demo some of these sophisticated front- and back-end frameworks, mail morphle at ziggo dot nl.

[1] https://www.seaside.st

[2] https://www.piercms.com/

[3] https://squeak.js.org

[4] https://caffeine.js.org

[5] https://lively-kernel.org

[6] https://croquet.io

[7] https://smalltalkzoo.thechm.org

[8] https://en.wikipedia.org/wiki/Dabble_DB (aquihired by Twitter)

[9] https://news.ycombinator.com/item?id=23191147