Section 1: Fireworks and Flags - Problem Understanding & Clarifications

Executive Summary: This section covers the first ten minutes of the interview, while the prompt is still two sentences long. We decompose live reactions and raise hand across what, who, why and how, run a clarification exchange in which every answer adds or removes real work, and arrive at the observation the whole module turns on: the two features look identical on screen and behave as opposites underneath. A reaction is a firework you are allowed to lose. A raised hand is a flag you must keep. We close by writing the assumptions down so every later section can cite them.

The interviewer turns their laptop toward you and reads aloud:

"Design the live reactions feature in Microsoft Teams meetings: a participant clicks applause, like, heart, laugh or surprised, and everyone in the meeting sees it float across their screen. Then extend your design to support raise hand."

It sounds like one feature with a bonus: five emoji buttons, then a sixth shaped like a hand. Many candidates build a tidy fire-and-forget pipeline for emoji, then bolt on raise hand as "one more reaction type." That is the trap. The two features share a button bar, a socket and a screen, and disagree about almost everything else.

Key Insight: The second sentence of the prompt is the interview. Reactions test whether you can build something fast and cheap that is allowed to fail. Raise hand tests whether you can add ordered, durable, shared state to that same pipe without breaking the first feature.

Decomposing the Prompt

Before asking anything, map the territory out loud.

• What it does: Reactions have two verbs, send and see. Raise hand has four: raise, lower, see the queue, and lower someone else's. That asymmetry is already a hint.
• Who uses it: Attendees react and raise hands. Presenters watch reactions land and work through the queue. Organizers and moderators can lower other people's hands, one at a time or all at once. Phone dial-in callers have no screen to click.
• Why it exists: Reactions are feedback without unmuting. A thousand people cannot all say "great news" into their microphones, but they can all clap. Raise hand is turn-taking and moderation, and it is an accessibility feature: it gives a voice to people who cannot easily interrupt, like the person on a laggy connection whose "sorry, can I..." always lands a second too late.
• How it's used: Reactions are bursty, a whole room clicking within the same few seconds. Hands are sparse and deliberate, and each one matters to the person who raised it.