I had to transfer 50TB+ to a new bucket with several rules based on the file metadata. Scanned all the file names, put them in a queue, then ran a custom C# program on several of the largest instances to process the queue. Maxed out CPU and bandwidth and it worked great.

I don't recommend Ruby for anything beyond the simplest websites. Don't try to make it perform, just use a better language that can handle the performance you need.