Preheat your oven to 350°F. Combine graham cracker crumbs, melted butter, and sugar in a bowl. Mix until the crumbs look like wet sand. Press the mixture firmly into a pie dish. Make sure the bottom and sides are evenly covered.

Place the crust in the oven. Bake for about 8 minutes until lightly golden. Remove it from the oven and let it cool completely. A cooled crust helps the filling set properly.

In a large bowl, whisk together the sweetened condensed milk and egg yolks. Continue mixing until smooth and creamy. Add the key lime juice and lime zest. Stir well until everything is fully combined.

Pour the lime filling into the cooled crust. Spread it evenly with a spatula. Make sure the top is smooth. This helps the pie look beautiful once it is finished.

Place the pie in the oven. Bake for about 15 minutes. The filling should look mostly set but still slightly soft in the center. Avoid overbaking to keep the texture creamy.

Remove the pie from the oven. Let it cool at room temperature for about 30 minutes. Then place it in the refrigerator. Chill for at least 3 hours before serving.

Before serving, spread whipped cream over the pie or add decorative swirls. Sprinkle extra lime zest on top. Garnish with lime slices for a fresh and colorful finish.