This is now about the 3rd or 4th year in a row I have used CDKEYS to renew my Xbox Live membership, and every time, I get the code within seconds, and it works on the first attempt. The price at CDKEYS is ALWAYS cheaper than renewing directly with Microsoft. Years ago, I was skeptical to make my first purchase. However, they have only become faster over the years, making it so easy to come back every year.
If this is your first time looking to buy, don't worry, you will not be left worrying whether you will get what you ordered or not. It will come through.