I applied online and heard back from the recruiter a few weeks later. It was a pretty standard process of talking to the hiring manager, a technical phone screen, an onsite interview, and negotiation.

The questions were pretty standard fare for an engineering-driven startup. I would recommend getting a copy of Gayle Laakman's "Cracking the Coding Interview" and practicing the questions involving standard data structures.

It's also helpful to be able to use various features from Java 8, such as streaming and lambda functions.

As others have mentioned, they have a coding behavioral interview. They want to get a feel for how you code, how you approach solving problems, how you prioritize work, etc. Make sure you're able to provide good answers with examples for those questions.

To show your interest in their engineering culture, I'd also recommend reading their engineering blog at eng.wealthfront.com.

Aside from the technical aspect, as a mission-driven startup, they want to get a feel for whether their mission resonates with you. Be sure to do your homework on their product and be able to speak to what you like about it (there are tons of blog posts on their website to help with this). Bonus points if you can ask questions about why they do XYZ differently than their prime competitors.

What is your approach to testing code?