System Design Interview Questions

S R. - "Wrote up a simple cache system using python dict. Added TTL requirement. Then went into code-level concurrency issues for the cache."See full answer

Shivastuti K. - "For somebody who needs accessibility accommodation, this doesn't have a transcript so it is not useful to me."See full answer

K S. - "Which location you were interviewed? Can you please share some details?"See full answer

Eshan P. - "Background A. Objective Lyft has a presence in Toledo, Ohio. At our current revenue per ride of $6, we can match 60% consumers requesting a ride with a driver. Our goal is to maximize net revenues in the next 12 months by figuring out the optimal revenue per ride. B. TLDR Summary · With a target market of (~100K-138K) consumers, on a $25 charge to consumers, Lyft should pay $20.75 to drivers and fix its share at $4.25 to maximize its net revenues over a 12-mont"See full answer

Sai vuppalapati M. - "At a high level, the core challenge here revolves around building an effective recommendation algorithm for news. News is an inherently diverse category, spanning various topics and catering to a wide array of user types and personas, such as adults, business professionals, general readers, or specific cohorts with unique interests. Consequently, developing a single, one-size-fits-all recommendation algorithm is not feasible. To enhance the personalization of the news recommendation algorithm,"See full answer

Teja G. - "To design a scalable ticketing system for peak events like Black Friday, you must employ a microservices architecture, implement robust load balancing, leverage caching, and use a combination of NoSQL and relational databases for different data types. Key features also include real-time seat booking, secure payment integration, mobile compatibility with QR code validation, robust admin dashboards for analytics, and integrated marketing tools like promo codes. The system needs to prioritize avail"See full answer

Michael F. - "Prompt: We work for an online shopping website. Our team wants to consider offering discounts (e.g. 10% off your next purchase) to customers to incentivize them to make purchases. How would you design a system that decides how to offer these incentives? Answer Goals: Increase customer engagement while controlling costs. Specifically, we want the increase in revenue per customer per week of customers that receive the discount to be greater than the cost of the discount. Metrics: Revenue per cu"See full answer

Dinar M. - " Thanks a lot for showing us how a recommender system can be build. I see it was proposed to use Collaborative filtering which is user - item matrix having dimension N * M (where N - number os users and M - number of songs). Though, it was explained how it gonna be built, it is still unclear how all users and songs features are going to be used. In that matrix we have values in cell (lets say i, j) like 1 - a specific user (i) clicked on song (j) when it was recommended or it is 0 when the user"See full answer

Kiran M. - "I started off with developing microservices for the game and then incorporating kafka to make it scalable"See full answer

Yashasvi C. - "I would first like to clarify the requirements and assumptions for the system. I am assuming that the system should support basic file operations such as uploading, downloading, deleting, renaming files, and viewing directory structures along with file permissions. The file size can range from around 1MB to 1GB, and the system is expected to be read heavy, meaning downloads will be more frequent than uploads. The system should support a large scale, for example around 10 million total users with"See full answer

Aymen D. - "It would have been more interesting to focus on the system design rather than the Trie DS, Interviewee could have just mentioned the Trie and passed to things more important. Interviewee should have focused on the factors on which he wants to scale the API servers, popularity of the query parts ? region may be ? A hash of many factors ? Caches should have definitely be discussed, Cache eviction policies, Cache invalidation managements... Interviewee should have mentioned which kind of API pro"See full answer

Alok S. - "Functional Rquirements: User should be able to read account balance user should be able to withdraw money from account user should be able to add money to account user should be able to create a new account user should be able to cancel an opened account All of the above for Checkings and Savings account User should be able to pay credit card bill (similar to adding balance to checking and savings account) Non functional Requirements: ACID transactions. consistency > availabi"See full answer

Karthik R. - "Good Discussion on the distributed messaging queues (Complex topic with lot of nuances) Liked the mind-map style drawing of requirements and metrics capture Touched on different types of queue styles (point to point, pub-sub, fan-out/fan-in) Storage and WAL usage was interesting Some distributed queue challenges that could be helpful to highlight / expand are: Message guarantee / semantics - Ordering of messages across different servers Replication Master slave architecture or Pe"See full answer

Eduardo C. - "I started asking some questions regarding the constrains of the system: An antena is emitting a signal that says if the tagged device was out of the room where the interview was happening. I was able to decide which would be the schema for the Antena's message. The antena is sending the info of multiple users. The system doesn't need to push notification to the users when the user left the device behind. Upon reflection, this is what I recollected doing. I propuse the json schema a"See full answer

Nitika B. - "Equation: Cost = Amount of storage required per year * Cost per year * 3 Amount of storage required per year = DAU * Storage requirement/user * 365 Assumptions: Cost per year = $99 = $100 Smart phone growth rate = 2% (But negligible at Pixel level) Annual Smart phone users = 2.8B Android users = 76% Google Pixel users = 1% Total Users = 2.8B * 0.01 = 280M *0.01 = 2.8M Method 1: Cost = Active Users + Cost/year * Number of years Cost = 3* 2.8M * $100 = 8.4M*100 = $840M Cost = $8.4B Method 2: C"See full answer

Pathworks P. - "To answer this, I will focus my efforts on explaining the most common type of API used in most modern software development applications - the REST API. For the purpose of simplicity, I will also keep the topics of Authorization and Authentication out of the mix. In essence, an API is a group of logic that takes in a specific set of inputs and responds with a specific set of outputs. This is analogous to going to a drive-thru and placing an order for a meal. When you give an API a bunch of"See full answer

San S. - "How might the system design change if it is limited specifically to a web/mobile use case?"See full answer

Ushita S. - "The back-of-the-envelope calculation is very well done!"See full answer