System Design Interview Questions

Anonymous Hummingbird - "Clarifying questions: Q: So FB locals is a standalone app that has reviews of local businesses? What is the current state of the product? A: Yes. It recently relaunched and branded. Facebooks mission is to connect people and help them build community, FB local fits into this by using the power of the large social network to surface businesses and events and uses signals such as reviews to build trust and provide value. So its of the utmost importance that the reviews are authentic. Goal: I"See full answer

Qusai B. - "Assumption: I’m estimating the minimum number of trains required to fulfil maximum demand I’m including all trains that’s serving NYC Formula: Before I state my formula, I would like to mention a few things I will be calculating the number of trains required to fulfill all demand at the peak time during a workday. I assume peak time lasts for 2 hours I’m assuming that a train takes 2 hours to complete one roundtrip on its route, which means any given train can service rider"See full answer

Clayton P. - "I've watched all the ML Systems designs interviews and this solution provides a clean baseline for predicting ETA using historical averages, but it falls short of addressing the broader problem of route planning. The system predicts ETA for a given segment and time interval, but it doesn’t explain how to compute the ETA for an entire route or how to integrate this into dynamic path selection. It also lacks depth on handling real-time data, adapting to distribution shift, or reacting to sudden"See full answer

Yomna H. - "Evication Strategy: LFU Access Pattern: Write Around"See full answer

Nilanjan D. - "Amazon Prime will generally have a limited group of uploaders rather than a million of them. This should influence the design of the Uploader service as it doesn't need to scale that much. Also the Encoding service role was not too clear"See full answer

Amit T. - "Question Design a product for P2P borrowing & lending money Clarifications Is this only P2P borrowing/lending or can financial entities participate too? - P2P only Is it to borrow/lend physical cash/digital money/cryptocurrency? - digital fiat money Are we focusing on specific geography? - US What’s the goal of this product? - Retention Are there any resource constraints? - No What’s the timeline to launch MVP? - 6 months FB Mission Empower people to build commun"See full answer

Luca D. - "The real discussion was very much similar o what exposed at https://www.tryexponent.com/courses/software-engineering/system-design/design-rate-limiter, but - as I commented the video - the real interviewer wasn't so naive to do not forgive the client identification only because IP. I had to introduce glimpses of https://en.wikipedia.org/wiki/Knowyourcustomer practice, I quoted JWT. I proposed a logical map of id addressing a "deque" of time-stamps of requests, with a threshold for the deque an"See full answer

Yag S. - "I studied Exponent's TinyURL system design video. My interviewer was asking many detailed questions on API design, schema, as well as data required to store. I found system design questions are bit high level instead of depth. I think should have detail design of API, schema and some additional flavors."See full answer

P K. - "Note: Modifying the question to reflect the storage cost as well. Question: Estimate the cost of storing google photos on the photos app? Clarifying questions: Google photos - an app that syncs automatically to your camera app and uploads photos to Google cloud and reduces the need to store it on your device Cost of 1GB storage $0.002 Time storage cost per year Equation: Cost of storage per year = average cost of storing photos per day x 30 days x 12 months The ave"See full answer

Anonymous Capybara - "using a relational database isn't a good choice for this system! we need more availability here than consistency (CAP theorem)"See full answer

Anonymous Jellyfish - "Microservices for resolving diffs, storage S3 for keeping files"See full answer

Kai W. - "The user awakes Alexa by saying the "Alexa word" Device starts recording audio from the user, and streaming it to the Alexa Cloud Service The recorded audio stream is sent to the ASR (Automatic Speech Recognition) system ASR returns the words and the order of the words in the audio stream, and sends this information to NLU (Natural Language Understanding) NLU returns the intent of the audio stream, and sends it to Alexa Skill If the intent triggers a "play" directive (e.g. turn"See full answer