Preheat your oven to 350F (180C).
In a small bowl, mix the graham cracker crumbs, granulated sugar, and melted butter together. Stir well until the mixture resembles wet sand.
Pour the crumb mixture into an 8 to 9.5-inch pie pan. Use your hands to press it firmly into the bottom and slightly up the sides of the pan.
Bake the crust in your preheated oven for about 10 minutes. Remove and allow to cool completely.
Add softened cream cheese to a mixing bowl and beat it well with an electric mixer until smooth.
Add both cans of sweetened condensed milk, key lime juice, and lime zest. Mix until smooth.
Pour the filling into the cooled graham cracker crust and spread it evenly.
Bake for an additional 10 minutes to set the filling.
Allow the pie to cool for 30 minutes, then refrigerate for at least 3 hours until set.
Whip the heavy cream in a mixing bowl until soft peaks form, gradually adding powdered sugar and vanilla.
Spread or pipe the whipped cream over the top of the cooled pie.
Slice and serve your delicious Key Lime Pie.