Food for thought, sometimes I wonder is the blockchain or the hosting site that is congested.
From a technical point of view, as an entity like a coinbase, they should have the capacity to scale their hosting site to meet the traffic demand. Millions of user is not even near to any fraction of what facebook is bomb at.
If it were the blockchain that is slowing it down, the hosting site shouldn't be freezing.
Technically when you send coins to the exchange, the exchange will cold store your coins and in return gives you their token of a representation of that coin you sent. Likewise for fiat. So, when you buy and sell, you are technically trading the exchange fiat token instead of the real coins and fiat.
yup, that make sense. I have once encounter trying to buy coin, yet got denied. Is frustrating. Likely was due to how popular the coin is and they run out of token, or reserving not to let us ride on the bull wave.