System Design Interview Questions

Rama A. - "1. What is an LFU Cache? An LFU (Least Frequently Used) cache is a memory management system with a fixed capacity. It tracks how often items are accessed and evicts the least popular items when it runs out of space. It has one critical rule and one tie-breaker rule: The Core Rule: When the cache is full and you need to add a new item, you must kick out the item with the lowest access frequency. The Tie-Breaker (LRU): If multiple items share that same lowest frequency"See full answer

Joshua K. - "Constrain is the inbound link, so the solution is to download the file once and then distribute it internally, rather than having every machine hit that link independently. So this may call for a central staging node and p2p distribution (bit torrent style)"See full answer

Kartikeya N. - "Clarifying questions: What is meant by abuse?: Fake, paid reviews Are we looking at any particular country ? : Global Have we seen an increase in the number of fake reviews on Amazon?: Yes Can we quantify the % of fake reviews and how much it has increased in the recent past?: Can’t divulge company data Lets first start with the Vision of Amazon. It is to be the world’s most customer centric company. That is a very lofty and high standards’ Vision. So the problem we are trying to s"See full answer

Alok S. - "Functional requirements: user can send an input and wait for the result Group up to 100 individual requests in to single GPU The system should should send results back to the user who requested it when done Non functional requirements: Minimize the waiting between two batches of execution/ reduce idle time error message if a batch faiils Scale to support multiple GPUs Core Entities: Request Batch Result API Design: POST /predict -> {requestid: "", response: ""} req"See full answer

Divya G. - "Designing a web-based word processor like Google Docs requires a robust system capable of handling real-time collaboration, high availability, and massive data consistency. 1. High-Level Architecture The system follows a microservices architecture to manage different concerns independently: Client Side: A web or mobile application that handles the UI and local state. Load Balancer: Distributes incoming traffic across multiple web servers to ensure high availability. **Web Serve"See full answer

Varun G. - "Constrain the requirements (The final product should be somewhat like Neptune AI and also enable for A/B testing) Do some back of the envelope calculations Start explaning your system with appropriate architecture diagrams Optimize for scale Answer any questions Wrap-up"See full answer

Theodore (teddy) W. - "So here is what I would do if I had to designing a system to log messages in order involves several considerations, including the choice of software, hardware, storage mechanisms, and scalability. Here’s how I would approach this: 1. Requirements Analysis: Message Format: Define the structure of the messages to log (e.g., text, JSON). Volume: Estimate the expected volume of messages per second. This will help in determining the infrastructure requirements. **Order Guarantee"See full answer

Tracy M. - "ingestion, processing & storage layer to handle document processing client ->API gateway/entry point->object storage-> queue-> worker-> database data flow: client initiates document upload + status processing API gateway (upload endpoint: authenticates & authorizes request, creates pre-assigned url to upload document); status endpoint object storage - stores uploaded document unstructured data (images, pdfs, docx etc) via preassigned url Message queue to decouple ingestion from proc"See full answer

Ajay P. - "Designing an evaluation framework for ads ranking is crucial for optimizing the effectiveness and relevance of ads displayed to users. Here's a comprehensive framework that you can use: Define Objectives and Key Performance Indicators (KPIs):** \\Click-Through Rate (CTR):\\ The ratio of clicks to impressions, indicating the effectiveness of an ad in attracting user attention. \\Conversion Rate:\\ The ratio of conversions (e.g., sign-ups, purchases) to clicks, measuring how well"See full answer

Vijay M. - "Very well done."See full answer

Mathursan B. - "Each song has a playback event that stores information (region, timestamp, etc.) and push to real-time streaming platform and eventually lands into data storage where another service could consume is periodically(say every minute) to compute aggregate counts for the last 7 days. The system can then fetch the top 10 songs by sorting based on playback events using timestamp, optionally filtered by region or genre."See full answer

Adam L. - "Discussed: Requirements of the system: latency language modality (assume keyboard typing) availability of data (assume cold start) success metric (accuracy of next word predicted?, or minimize false positives? -> accuracy to start) Data collection and processing: design ethical user experiments to collect typed out data design a simple tokenization strategy (word level encoding, character level encoding, byte-pair encodings, and discuss tradeoffs) collect data, and split"See full answer

Anonymous Mongoose - "The below system design addresses the requirements for a scalable distributed onboarding service, focusing on robust data validation, asynchronous processing, real-time aggregation, and efficient querying of metadata. Core Principles: Asynchronous Processing: Decouple components to ensure high throughput and responsiveness. Scalability & Elasticity: Utilize technologies that can scale horizontally to handle varying loads. Data Durability & Integrity: Ensure no data l"See full answer

Anonymous Hummingbird - "Clarifying questions: · Is there a specific scenario we are building before? Example: urgent need for a specific type of blood vs building up blood banks proactively. You decide · This would be for mobile/web and integrate into the existing facebook product? Yes Ok before we get started I wanted to discuss the facebook mission: to give people the power to build community and bring the world closer together. I can see how blood donation fits directly into this, enabling blood donation helps"See full answer

Jaehyuk C. - "Q: What ad system do we have (to clarify the limitation of the ads systems and its scope)? -> need context of the advertisement. What signals of ads do we have? pictures, texts, comments, video, etc. What is daily active users on the system? (scalability) Do we need taking actions after detecting it? (further process is needed?) what device do we have ad system? PC, mobile, etc. FR: detect the weapon signals (classification) alert after weapon is detected identify the us"See full answer

Ekta M. - "I would start with some clarifying questions like: Is there a deadline when all these needs to be updated by? Do we have upgrade scripts ready? When do we have change freeze? Once I have these few clarifying answers I would start planning: I would meet with all the teams involved in the upgrades Document any resources downtime during the upgrade create a risk registry along with mitigation plan Roll back plan create a phased rollout plan based on deadline Post upgrade get a"See full answer

Palak A. - "Designing a system to deny services to requests from banned IPs involves integrating real-time IP checking with your service architecture. Here’s a detailed outline of how you can design such a system: System Design Overview The goal is to ensure that your service can efficiently check incoming requests against a list of banned IPs and deny access when necessary. The system will leverage an external API, security.gov.x, to determine if an IP address is blocked or allowed. **Key Compone"See full answer