In a medium bowl, combine the graham cracker crumbs and melted butter. Mix until the crumbs are evenly coated. Press the mixture firmly into the bottom of a 9-inch springform pan to create the crust. Chill in the refrigerator for 15 minutes to set.

In a large mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy. Gradually add the powdered sugar, mixing until well combined.

Add the sour cream, key lime juice, and vanilla extract to the cream cheese mixture. Mix until smooth and fully incorporated.

In a separate bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the key lime mixture until no streaks remain.

Pour the cheesecake filling over the chilled crust and spread it evenly. Smooth the top with a spatula. Cover the cheesecake with plastic wrap and refrigerate for at least 4 hours, or overnight for best results.

Before serving, garnish with lime zest and lime slices. Carefully remove the sides of the springform pan and slice the cheesecake into wedges.