Sizing the yearly cloud storage footprint of Google Nest camera video

Estimate how much memory Google's Nest cameras needed over fiscal year 2020. The prompt leaves the key terms open, so first agree with the interviewer on what "memory" means and what the estimate should cover. Then build it: write the equation, state each input as a labeled assumption with a round number, carry the arithmetic through in consistent units, and sanity-check the final figure. ```hint Split before you multiply Cameras differ in how long their video is kept and in whether they save only short clips or record nonstop. Group the cameras by what they keep and for how long, and estimate each group on its own before adding them up. ``` ### Clarifying Questions - By "memory," do you mean the cloud storage that holds recorded video, the storage inside the cameras themselves, or something else? - Should the answer be the storage that must exist at one time, given how long video is retained, or the total amount of video written during the year? - Which cameras are in scope: every Nest camera active during 2020 or only units sold that year, indoor and outdoor cameras only or video doorbells too, and in which countries? - What does each Nest subscription tier keep, and for how long, and what is stored for a camera with no subscription? ### What a Strong Answer Covers - A settled definition of the quantity (storage held at one time versus video written over the year) and of the scope: region, camera types, and installed base versus 2020 sales. - An equation that segments cameras by retention window and by event-only versus continuous recording. - Labeled, defensible assumptions for the camera count, events per day, clip length and video bitrate, with the arithmetic carried through without unit slips. - A sanity check against an independent reference point and a view of which inputs move the result most. - Translation of the logical figure into capacity to plan for, including redundancy and growth during the year. ### Follow-up Questions - One term in your equation dominates the total. Which one, and what product or engineering changes would shrink it the most? - How would you turn the storage figure into a yearly cost and compare it with what camera subscriptions bring in? - If the interviewer wanted every country where Nest cameras are sold, how would you extend the estimate without redoing it from scratch?