Hello guys,
we are know those big exchange platforms like Binance, Kraken, Coinbase, etc, where you need to register, pass a complex KYC process and then you get to a complicated dashboard where you basically need to set an offer for your coins and wait someone to accept it. Anyway, the instant crypto exchange is something else. It's a website where you can directly exchange Coin A to Coin B from your wallet to your wallet. The trades are usually taking few minutes and there is nothing complicated about the interface. You literally need a source wallet(where you will take the crypto from to trade it) and a target wallet (for the coins you will receive from the exchange). Those exchanges due to the big completion on the market are often very cheap and easy to use.
So far I have used 3 of them and can guarantee to be legit and working. I will not go deep explaining about them, just because all of them are doing exactly the same thing. All of them can be used even without registration, but if you register you can benefit from some other features they have such as referral program. Also those instant exchanges have APIs that are often integrated in some of the desktop wallets we use.
Here is the list:
1) Changelly. This is the oldest I know. I used it for the first time back in 2017 when I wanted to exchange my mined rewards in XMR and ETH to Bitcoin. Nawdays I use it less often when I want to get some coins that are not listed on Coinbase.

There is referral program that you can join if you decide to register under my link here: https://changelly.com/?ref_id=4bbd973f4c57
The rewards from it are percent of the trades from the guys you invited are doing. Never used it personally.
Or simply go to https://changelly.com
2) SimpleSwap is an instant exchange with loads of supported currencies, 90% revenue sharing via the referral program and their own SWAP token, about which you can read on their website.

I was actively using this platform while I was mining Calisto (CLO) sometime ago, because they were one of the first exchanges to list it. There are many other assets that can be found here and traded without the hustle of registrations and high fees and so on. I have no affiliate link since I never bothered to register there, but you can check the exchange here -> https://simpleswap.io/.
3) Shapeshift.io is another platform with the same type as the previous two, but with relatively smaller pool of accepted coins/tokens. I offer free of charge trades if you are holding some of their FOX tokens.

Using their other features might be beneficial, but for me the best part is that you are able to just open the website, enter the addresses, send the coins and directly have the received amount in your wallet without the hastle of registering, completing KYC, 2FA authentications and so on. Sometimes this really gets on my nerves.
I hope you guys find this useful.