My does that kind of "stuff", we automatically convert audio and embed inaudible watermarks to prevent piracy,leaking, etc. AWS makes a lot of the concurrency

My does that kind of "stuff", we automatically convert audio and embed inaudible watermarks to prevent piracy,leaking, etc. AWS makes a lot of the concurrency issues easy (and scaling). Basically you can use their SQS ("Simple Queue Service"), add tasks to it, and when the individual drones check out a song from the queue, it's no longer available for a set amount of time. If the drone finishes the process completely, it removes it from the queue permanently, but if the drone fails, dies, whatever, after that time-out it gets bumped back into Queue for the next worker drone. We use FFMPeg for conversion. --- note: tracktrack.it, if you're curious about watermarking.