In a small mixing bowl, combine the graham cracker crumbs with the melted butter. Stir thoroughly until the crumbs are evenly coated and resemble wet sand. Transfer the mixture to a 9-inch pie pan and press it firmly into the base and up along the sides to form a compact crust. Use the bottom of a glass or measuring cup to smooth and level the surface for a clean edge.

Place the softened cream cheese into a large bowl. Using a hand mixer, beat the cream cheese on medium speed until it becomes silky and lump-free. Slowly pour in the sweetened condensed milk and key lime juice. Continue mixing until the ingredients are fully incorporated and the filling is smooth and slightly thickened.

Carefully pour the filling into the prepared graham cracker crust. Smooth the top with a spatula to create an even surface. Place the pie in the refrigerator and chill for at least 1 hour, or preferably overnight, until the filling is firm and set.

Just before serving, garnish the pie with fresh slices of key lime and generous swirls of whipped cream for a bright, refreshing finish.