I think it's THE CAUSE not the potential cause @Juji
The live tracking of the rank based on gained exp is just causing to much stress on the server. The game is doing 2 ranking updates every time a player kills a mob, on Naia that is basically 2 database updates every second for 2000+ players. All lag issues in the past were caused by the database not being able to handle it. Years ago with the Piero event the item server lagged to a stand-still because to many items being dropped, same happened during almost every Valentines, Letters, Melon/Pumpkin event in the past 8 years.
Just disable the Ranking System permanently. It has no additional value to Naia nor Chronos. The top 25 on Naia is populated by MAX and DH all level 109/110 gained from doing AFK macro exp since the last boost event and spending $15/h on boost items. All these guys don't need the buff the system is giving to (not) fight each other. It's a system that adds no value to a disorganised server structure like the one our servers. The Ranking System only makes sense on Korean, Japanese, Russian and EU servers were people have the Premium Account system or similar monthly subscription services (Prestige Pack isn't one, it's a joke compared to other regions).