This is a crossover episode with the Law & Order: Organized Crime (2021) premiere episode, What Happens in Puglia (2021).
This episode also marks the first appearances of Isabel Gillies as Kathy Stabler, Allison Siko as Kathleen Stabler, and Jeffrey Scaperrotta as Dickie Stabler, since the episodes Delinquent (2011) (216 episodes earlier), Gray (2010) (230 episodes earlier), and Turmoil (2009) (255 episodes earlier), respectively.
This is Christopher Meloni's first appearance on the series since the season twelve finale, Smoked (2011), which was 215 episodes earlier.
The Central Personnel Index (CPI) is a computerized database that records and classifies all critical events in officer's careers, including complaints, departmental recognition, designations as chronically sick, and unfit for duty. It can be summarily described as "personnel folder" or "disciplinary records" for all active duty personnel.
Either by design or just a coincidence, the crossover aired the day before Christopher Meloni's birthday.