Rely on http caching instead of changing names, if you’d like the old gen server to not 404?
A common way to bust caches is to append a query string: asset.js?oldhex1 / asset.js?newhex2. In your case, if the request for newhex2 reaches old gen, then it is left for it to decide whether to serve a 404 or not.
Usually, one would not use explicit random hexes in query strings but instead rely on ETags (mdn), which almost all CDNs and blob stores support, along with Cache-Control directives.
Speaking of CDNs, I’d not use [[statics]] if I was looking for a http cache compliant delivery: Does Fly serve `Cache-Control` origin responses off of its edge cdn? - #2 by jsierles