Pokemon Let's Go Early Access FAQ

>What prevents us from getting into Let's Go Pikachu and Eevee early?
Two layers of protection.
-The games' content needs to be uploaded to the CDN.
-The games' titlekey needs to be made available (this is equivalent to saying the games must be released).

>What's a titlekey?
A titlekey is a 128-bit number, used to decrypt content that has been downloaded from the CDN.
Titlekeys are stored in Tickets, which your console receives once a title it has been purchased has been released.

>Nintendo made the games prepurchasable. Why can't we decrypt them? Your sun/moon FAQ says titlekeys are available on purchase, and I purchased the games!
On the 3ds, this would have been true -- purchasing a game on the 3ds always gives you its titlekey. To solve the preload problem there, Nintendo introduced "content lock seeds" -- data that is unavailable until release.
On the Switch, titlekeys work the way content lock seeds did on the 3ds. They are unavailable until release (instead of a ticket, your console gets a "PrePurchaseRecord" which does not have a titlekey in it).
Without the titlekey, the games can't be decrypted, even if you've installed them via pre-purchasing. Nintendo is not stupid, and has not and will not release this value to anyone prior to release.

>What does all this mean?
-The games will probably be uploaded to the CDN in the next day or so, as they are slated to be prepurchasable on October 22nd.
-The games will be protected by a 128-bit value, which nobody can brute-force before the universe dies.

All in all, nobody's going to be getting into Let's Go early via the eShop, because nobody has or will have the titlekey.