The interview process for a Senior Software Developer is focused mostly on System Design based on your past experience. As a senior developer, be prepared to describe, in detail, a problem you have solved recently and answer any technical follow up questions. The interviewing panel is knowledgeable and open minded about different approaches as long as you can justify your choices, tradeoffs and constraints. Also, be prepared to describe how you would solve a given technical system design problem. The overall interview process was a great experience for me and I recommend any software developer, who would rather talk about how they solved real life technical problems instead of completing toy problems online, to apply.
There are four stages in the interview process (ymmv):
1. Recruiter interview (30 mins)
2. Technical interview - Tech Lead (15-30 mins)
3. Technical interview - Panel (1 hour)
4. Leadership Skills/Values/Technical interview - Panel (1 hour)