In a mixing bowl, combine graham cracker crumbs, sugar, and melted butter. Mix until well combined. Press the mixture into a 9-inch pie pan, ensuring an even layer on the bottom and sides. Chill the crust in the refrigerator while you prepare the filling.

In a large mixing bowl, beat the softened cream cheese until smooth. Gradually add the sweetened condensed milk, mixing until fully incorporated. Stir in key lime juice, zest, and vanilla extract, blending until the mixture is smooth and creamy.

Pour the filling into the prepared crust, smoothing the top with a spatula. Ensure the filling is evenly distributed within the crust.

Preheat the oven to 350°F. Place the pie in the oven and bake for 15 minutes, or until the edges of the filling are set. Avoid overbaking as the center should remain slightly soft.

Remove the pie from the oven and allow it to cool at room temperature. Once cooled, refrigerate the pie for at least two hours or until fully set.

Slice the chilled pie into 8 equal slices. Serve chilled, optionally garnished with whipped cream or lime slices for added presentation.

Cover leftover pie with plastic wrap or place in an airtight container. Store in the refrigerator for up to three days to maintain freshness.

To freeze, wrap the pie tightly in plastic wrap and then in aluminum foil. Store in the freezer for up to one month. Thaw overnight in the refrigerator before serving.