A hot wallet only contains about 5% of the bitcoins the company has.
Meanwhile, the other 95% of bitcoins they're holding are stored savely in a key-split cold wallet.
Now, the problem is: if some user wants a large amount of his bitcoins out of coinbase, the guys owing their part of the split private key need to take action to transfer that amount of bitcoins from the cold to the hot wallet, assuming the amount is > 5%.
So what I think "Vault" does is give them a better architecture for planing and organizing their hotwallet-coldwallet-process.
Brian Armstrong, CEO of Coinbase once said in an interview (http://techcrunch.com/video/coinbase-founder-brian-armstrong...) that they are dividing their bitcoins in hot and cold wallets.
A hot wallet only contains about 5% of the bitcoins the company has. Meanwhile, the other 95% of bitcoins they're holding are stored savely in a key-split cold wallet.
Now, the problem is: if some user wants a large amount of his bitcoins out of coinbase, the guys owing their part of the split private key need to take action to transfer that amount of bitcoins from the cold to the hot wallet, assuming the amount is > 5%.
So what I think "Vault" does is give them a better architecture for planing and organizing their hotwallet-coldwallet-process.