Start by combining graham cracker crumbs, melted unsalted butter, and sugar in a mixing bowl. Blend until fully incorporated and crumbly. Pack mixture into a 9-inch pie dish and place in the freezer for 15 minutes.

Mix gelatin with cold milk in a small bowl and let it sit for 5 minutes to bloom. Heat in the microwave for 15-30 seconds until gelatin dissolves completely.

In a large mixing bowl, blend cream cheese until smooth. Gradually add sweetened condensed milk and key lime juice, mixing until creamy. Fold in dissolved gelatin mixture.

Pour filling into the frozen crust, spreading evenly. Tap the pie dish on the counter to release any air bubbles.

Cover the pie with plastic wrap and refrigerate for at least 6 hours until set.

Before serving, top with whipped cream and garnish with lime zest or slices.