Amazon Interview Question for SDE1s

Team: Kindle
Country: United States
Interview Type: In-Person

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Assuming each camera captures 640 x 480 p video & all data stored in a raw format, its easy to do calculation that per camera storage requirement is around 10 GB of data per hour. The given spec matches. So we are good.

30 miles per hour of speed == 0.5 miles per sec. Since cameras are placed at 0.3 mile, a moving vehicle will always be captured every sec by a new camera.

Db Design - Either cameras are doing OCR to figure out numbers at camera level, or the video is being stored on a central server where OCR is being done. For every frame, if a vehicle is identified, the number plate, timestamp & camera id is stored. I will index the DB on number plate. So for a given number, query can be done such that all rows with the number plate can be fetched ordered by timestamp. This way, the path of the number plate can be easily traced.

- Ashish October 21, 2016 | Flag Reply

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