If a plaintiff does not serve the summons and complaint within 120 days of commencement of the action, "the court, upon motion, shall dismiss the action without prejudice as to that defendant, or upon good cause shown or in the interest of justice, extend the time for service." Good cause and interest of justice are two separate and independent standards. In order to establish good cause, a plaintiff must demonstrate reasonable diligence in attempting service. The interest of justice is a broader standard meant to accommodate service that is late due to mistake, confusion or oversight, as long as there is no prejudice to the defendant. The interest of justice standard requires a careful judicial analysis of the factual setting of the case and a balancing of the parties' competing interests. Under the interest of justice standard, the court may consider diligence, or lack thereof, along with any other relevant factor in making its determination, including expiration of the Statute of Limitations, the meritorious nature of the cause of action, the length of delay in service, the promptness of the plaintiff's request for an extension of time, and prejudice to the defendant.
Nationstar Mtge., LLC v. Wilson, NY Slip Op 07595 (2d Dep't October 23, 2019)
Here is the decision.