It really, really depends on the technology. Moving JavaScript to TypeScript or PHP to Hack is easy by design. The new technology is built specifically to allow you to migrate the old technology gradually.<p>Angular 1 to 2, on the other hand, wasn&#x27;t designed to be an easy transition. They&#x27;re very different frameworks.<p>So to answer your question, I use a new technology that allows gradual transition (when possible), or I use &quot;free&quot; time to do a full rewrite. If I find enough time to make something stable enough to move into production, great; otherwise, I&#x27;ve demonstrated empirically that we don&#x27;t have enough time to invest in a transition.