Vibe Coding and System Design

The vibe-coding session and the agentic system design round are the two parts of the Google FDE loop that candidates find most demanding. Neither has a single correct answer, and both begin with a brief that is deliberately incomplete. The interviewer is not checking whether we reach a predetermined solution. The interviewer is watching how we turn an ambiguous request into something that works and holds up under real constraints.

Both rounds reward the same working habit: clarify the problem, scope a first version, build something that works, and adapt as new information arrives. The sections below turn that habit into two practical frameworks, starting with the vibe-coding session.

How the vibe-coding session works

The vibe-coding session is a 60-minute collaborative build. The interviewer presents a short brief and then works through the problem alongside us, much like a pair-programming partner. AI-assisted coding tools are often permitted, and that changes what the round measures. When a tool can generate most of the code, the signal shifts away from typing speed and toward judgment: what we choose to build, how we verify it, and how we respond when the direction changes.

During the session, the interviewer may suggest an approach, ask us to justify a decision, or change a requirement partway through. These interruptions are part of the format. They simulate a customer who learns something new during a working session and asks for a change. Because the setup varies, it is worth confirming with the recruiter whether AI-assisted tools are allowed and which environment the session uses, then practicing in a similar setup beforehand.

With the format clear, the next step is a framework for handling it.

A framework for the ambiguous build

A reliable ...