In applying a mandatory sentence in a drug conspiracy case, does Alleyne v. United States, 570 U.S. 99, 133 S.Ct. 2151 186 L.Ed.2d 314 (2013), when read in conjunction with United States v. Rowe, 919 F.3d 752 (8d Cir. 2019), require the government to prove that the defendant conspired to actually possess the threshold amount at a given time, rather than rely upon an aggregation of drug quantities over the course of the conspiracy?

Whether the government must prove the defendant conspired to actually possess the threshold drug amount at a given time, rather than rely on an aggregated drug quantity over the course of the conspiracy