Yarn and Npm are package managers. They are not build automation tools. They only pull dependencies and publish them back and perform dependency resolution. Le

Yarn and Npm are package managers. They are not build automation tools. They only pull dependencies and publish them back and perform dependency resolution. Lein and Boot are full build tools. They do package management, but they also do task automation such as Gulp and Grunt, bundling such as Webpack and Parcel, and scaffolding such as Yeoman or Brunch. If you take only their package management subset. Then it does take only 15 min to switch from one to the other. Just like Yarn and NPM both publish too and pull from npm repositories, Lein and Boot publish too and pull from Maven repositories. It is only once you get to task automation that Lein and Boot start to differ. Rewriting your tasks and build pipeline from one to the other will take you much longer. That's also true of switching from Gulp to Grunt for example. I also want to add that, bundling is similar in Boot and Lein. While the tasks to do so are not, the way things are bundled is the same. Scaffolding is also interchangeable, since both support each others template formats.