About Optimizing Querying Posts by Custom Fields

Hi all

first .. sorry 4 my english ??

i am web developer and using wordpress as framework for any Customized CMS i want build

if i want to make a video Cms for example and want to make keys for videos instead of ID’S

each video is post has ID , and Customfield ( “vkey” => “1A2B3C” )

each post will have the customfield ( “vkey” )

so i want to make a custom page to view video by key

example.com/vid/ANYKEYHERE

will take the key and QueryPost it

my question here
if i will have more than 1,000,000 Videos [ POSTS ]

i looked up at (“POSTMETA”) table structure @ wordpress database
and ofcourse they cant make this field (“UNIQUE”)
or Indexed coz this field may have alot of similar values like values of key ( _edit_last )

so i think the query will look at all (“vkey”) values to find the one matching the Key comes from URL

i ask about this coz this page will be the most visited page at the cms and we will have alot of visits when we lunch it

i hope that any body can get what i talk about .. coz i know my bad english ??

Thanks in Advance