I think it would be great to have the option to do parallel downloads of packages, with a configurable amount of threads. Something like “apk —no-cache —parallel=8 add openjdk8”. (with a default of 1)
You could also grab the various APKINDEXes using that same thread pool.

If you didn’t want to hammer the CDNs, you could add a hard-coded exemption to *.alpinelinux.org or something.

I’m running a local mirror of dl-cdn.alpinelinux.org, so I would really like to take advantage of my internal bandwidth.

Since all the dependency information is in APKINDEX, I would think it wouldn’t be too painful to throw it in a prioritized queue and delegate to an executor of some kind, but I haven’t looked at the internals (yet).

(from redmine: issue id 5977, created on 2016-07-27)