CPLR 5015(a) is a frequently invoked provision in New York practice. It lists the principal grounds on which a judgment or order may be vacated. It provides (verbatim) that “[t]he court which rendered a judgment or order may relieve a party from it upon such terms as may be just, on motion of any interested person with such notice as the court may direct, upon the ground of: * 1. excusable default, if such motion is made within one year after service of a copy of the judgment or order with written notice of its entry upon the moving party, or, if the moving party has entered the judgment or order, within one year after such entry; or * 2. newly-discovered evidence which, if introduced at the trial, would probably have produced a different result and which could not have been discovered in time to move for a new trial under section 4404; or * 3. fraud, misrepresentation, or other misconduct of an adverse party; or * 4. lack of jurisdiction to render the judgment or order; or * 5. reversal, modification or vacatur of a prior judgment or order upon which it is based.”

Siegel, N.Y. Prac. § 426 (5th ed.)

Not Every “Default” Qualifies for the Vacatur Motion of CPLR 5015(a)(1); If There Was Full Contest, Appeal Is Proper Route
The point is by no means new. We make it in the original Commentary at page 209 in the main volume. A good illustration of the competition between a CPLR 5015(a)(1) motion to vacate the judgment and an appeal from the judgment appears in Lauer v. City of Buffalo, 53 A.D.3d 213, 862 N.Y.S.2d 675 (4th Dep't, July 3, 2008).
When the one route is open, the other is usually closed. So, when is each open? If there was no contest at all, the motion to vacate is proper; if there was, then even if the judgment or order is denominated a “default”, appeal is the only route for to review. The Lauer case illustrates. It's treated in a