How do we review the sufficiency of a charging instrument de novo?

We review the sufficiency of a charging instrument de novo. United States v. Geibel, 369 F.3d 682, 698 (2d Cir. 2004). When, as in this case, the defendant fails to object to a purported Rule 11 violation before the district court, we review for plain error. United States v. Youngs, 687 F.3d 56, 59 (2d Cir. 2012). In so doing, we assume the parties' familiarity with the facts and record of the prior proceedings, which we reference only as necessary to explain our decision to affirm the district court's decision.