Line a muffin tin with cupcake liners.
In a medium bowl mix the graham cracker crumbs with sugar, melted butter, and salt, until well combined.
Place 2 tablespoons of the crumb mixture in the bottom of each cupcake liner. Press firmly with the back of a spoon or with your fingers, to pack the crust tightly.
Place cream cheese in a large bowl and beat on high speed for 2 minutes. This can be done using a stand mixer or hand mixer.
Scrape the sides, then add the powdered sugar. Mix on low speed until combined, then increase to high speed for 1 minute.
Add the vanilla, key lime juice and key lime zest and mix well.
Gently fold the whipped topping into the cream cheese mixture being careful not to deflate the whipped cream.
Fill the muffin cups with the cheesecake filling, spreading the tops to smooth.
Refrigerate for 4 hours, or overnight.
When ready to serve, top with dollops of whipped topping or use a large star tip and a decorator bag to pipe the topping onto the cheesecakes. Garnish with additional key lime zest.