DB Error: constraint violation

INSERT INTO cart (id_cart, id_user, id_session, id_plateforme, id_plateforme_pays, status, date) VALUES (6316569, 0, 'b115a6be120cb5b198f64611975d609f', '5', '8', 'session', NOW()) [nativecode=1062 ** Duplicate entry '6316569' for key 1]