Preheat your oven to 350°F. In a medium bowl, combine the graham cracker crumbs, sugar, and melted butter. Mix until the crumbs are fully coated and resemble wet sand. Press the mixture firmly into a 9-inch pie dish, using the back of a spoon or measuring cup to ensure an even layer. Bake the crust for 10 minutes until lightly golden. Remove from the oven and let it cool slightly while you prepare the filling.
In a large bowl, whisk together the egg yolks and sweetened condensed milk until smooth. Gradually add the key lime juice and lime zest, whisking continuously until fully combined. The mixture will slightly thicken as you mix. Pour the filling into the cooled graham cracker crust, spreading it evenly with a spatula.
Bake the pie at 350°F for 15 minutes. The filling should be set but slightly jiggly in the center. Remove from the oven and let the pie cool to room temperature. Transfer to the refrigerator and chill for at least 3 hours (or overnight) to allow the filling to fully set.
In a large bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract using a hand mixer or stand mixer on high speed until stiff peaks form. Spread or pipe the whipped cream over the chilled pie.
Garnish with a sprinkle of lime zest, lime slices, or a light dusting of graham cracker crumbs. Slice, serve chilled, and enjoy every creamy, tangy bite!