Preheat your oven to 350°F (175°C).

In a bowl, mix the graham cracker crumbs, sugar, and melted butter until well combined, resembling wet sand.

Press the mixture firmly into the bottom of a 9-inch pie pan to form the crust.

Bake the crust for about 8 minutes, or until lightly golden, then let it cool.

In another bowl, whisk together the sweetened condensed milk, sour cream, and key lime juice until smooth and creamy.

Pour the filling into the cooled crust and spread it out evenly.

Bake the pie for an additional 10 minutes, or until the filling is set but still slightly jiggly.

Let the pie cool to room temperature, then refrigerate for at least 2 hours.