The interview went through 5 phases with 5 different current employees:

Phase 1: Introductory phase, discussing my background, the job activities of the person administering this phase, etc.

Phase 2 - 4: Employees asked me some of Google's coding questions (I won't give specifics, as per the agreement). The questions were of average difficulty compared to the samples out there.

Phase 5: Another employee, whose background was close to mine, asked me specific questions about my former research.

They asked me a specific algorithmic question concerning my PhD research. The question was specific enough, and the interrogation did not go too deep because I think I satisfied the purpose: do I really know the details.