How youtube encodes video ids in urls?

Question

What's the encoding used for a youtube video url (the id part) ?

watch?v=fqgPmnW8yCU

And what's the advantage of using that instead of something like this

watch?v=video200

Other than protecting private videos, is there any? I ask because i'm thinking of the fastest/best way to return an image file (when i've got over 20,000 accessed regularly).

Answer 1

Most probable it's a hash. Given that, probably for the search part they use a hash map mechanism which provides a very fast and optimal search capability.