How decentralized is dYdX?

When it comes to assessing the decentralization of dYdX, it's important to delve into its underlying architecture and operations. Can you elaborate on how dYdX's decentralized exchange model differs from traditional centralized exchanges, and what measures the platform has in place to ensure a high level of decentralization? Furthermore, how does the platform's use of smart contracts and decentralized governance mechanisms contribute to its overall decentralization? Lastly, are there any limitations or challenges that DYDX faces in maintaining its decentralized nature?