[tluyben2]

Well, good ABI/API’s and, let me really clearly separate this from the word ‘good’, standard OS GUI frameworks like Windows wpf and Mac OS X cacao for frontends is as far Lego as I have seen for now. Web frontends is where it all goes terribly wrong; nothing fits and everything breaks when you put X into Y when X and Y are from other authors generally. It is a shit show. But for backends and internally it can be done with good APIs. Problem is… not many people can write those, so you end up with something that says lego on the pack but is in fact lego after your ‘always was a bit weird’ cousin played with it with his flamethrower.

[tengstrand]

Polylith targets the backend, so I will concentrate my answer around that. I agree that good APIs are important. Polylith helps you with sharing code because it's built around "movable"/decoupled bricks that can be reused across services (e.g. different kinds of APIs). Reuse is a hard problem to solve, and you need LEGO-like building blocks for that.