What network is dYdX on?

I'm curious to know which network the decentralized exchange dYdX operates on. With the vast array of blockchain options out there, it's important to understand which underlying technology powers a particular platform. Given the significant implications on transaction speed, security, and overall user experience, I'm eager to get a clear understanding of dYdX's network infrastructure. Could you elaborate on which blockchain dYdX is built on and why that choice was made? Additionally, are there any plans for expansion to other networks in the future? I'd appreciate any insights you can provide.