I think database implementation and distributed systems are really interesting and impactful areas of computer science. I'm really looking forward to learning about them.
I'll also get a chance to use Rust 'in real life'. It's hard to describe why that is a big deal for me; I've been programming in Rust pretty much daily for the last five years and writing real programs (and some pretty damn interesting ones too). But it feels cool to use it 'on the outside' after being 'on the inside' for so long. Especially in a project which is well-suited and committed to Rust.
I'm also a bit nervous - there's going to be a lot to learn (it's a big change in domains for me).
And I'll continue to work remotely from New Zealand, which is great, and really important to me.