Mock system design interview at HubSpot

A live 45-minute round on a question reported in HubSpot interviews, run by an AI interviewer that asks one thing at a time, probes what you say, looks at your whiteboard, and weighs what that round is reported to weigh. It ends with a debrief: a score, what was strong, what was missing.

your question

Design Zapier

Connect thousands of third-party apps: watch ten million triggers by polling or webhook, and run each new event through multi-step workflows on someone else’s APIs.

You will not see the requirements, the numbers or the design before you start. That is the point.

Walk through it first

What the HubSpot round is reported to look like

Usually two design rounds of about an hour each, and the prompts repeat: a weather service fed by an outside weather API, and a video streaming service like Netflix. HubSpot describes the round as mainly discussion, and you may not be asked to write code at all.

What it weighs

Clarifying questions first, and your thinking said out loud, as HubSpot advises for its technical interviews
Real knowledge of any technology you name, since interviewers drill into it
On the weather prompt: pulling from the outside API cheaply, caching, and data fresh enough for its users
On the streaming prompt: browsing and searching the catalogue, storing and caching the video, and adaptive bitrate

The common mistake

Giving the well-known answer and stopping. The weather and Netflix prompts are widely shared, so interviewers are reported to push past the standard design into details, such as how to avoid fetching the same weather data twice, and into any technology you mention.

From public interview guides and candidate reports, and HubSpot’s own interview guidance where it publishes any. Not endorsed by HubSpot. The interviewer is an AI running in that style; it is practice, not a prediction.

Start the round

Timed · 45 minutesInterview conditions. The AI interviewer owns the clock; the AI Mentor is off.With the AI Mentor · untimedNo clock, and an AI Mentor beside you to ask when you are stuck.

The interviewer’s opening question is free. Answering it is part of Pro. See an example round and its debrief →

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