Senior+ System Design Interview Questions
System design is the round that carries the most weight in a senior+ loop, and it's where senior+ candidates most often pass or fail. These system design questions were reported from senior-level interviews, so they reflect what interviewers actually push on at the senior+ bar: designing for scale, reasoning explicitly about trade-offs, handling failure modes, and driving the conversation instead of waiting to be led. Expect open-ended prompts — design a rate limiter, a news feed, a notification system — where the interviewer probes your bottlenecks and asks you to defend every decision. Each comes with a detailed model answer that walks through requirements, the high-level design, the deep dives, and the trade-offs a strong senior+ answer makes explicit.
"I got asked a hardcore MCM DP question and I saw it on PracHub as well. Solved that question in 5 minutes. Without PracHub I doubt I could solve it in 5 hours. Though somehow didn't get hired, perhaps I guess I solved it too fast? /s"
"Believe me i'm a student here jn US. Recently interviewed for MSFT. They asked me exact question from PracHub. I saw it the night before and ignored it cause why waste time on random sites. I legit wanna go back and redo this whole thing if I had chance. Not saying will work for everyone but there is certainly some merit to that website. And i'm gonna use it in future prep from now on like lc tagged"
"10 years of experience but never worked at a top company. PracHub's senior-level questions helped me break into FAANG at 35. Age is just a number."
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"Got a Google recruiter call on Monday, interview on Friday. Crammed PracHub for 4 days. Passed every round. This platform is a miracle worker."
"I've used LC, Glassdoor, and random Discords. Nothing comes close to the accuracy here. The questions are actually current — that's what got me. Felt like I had a cheat sheet during the interview."
"The solution quality is insane. It covers approach, edge cases, time complexity, follow-ups. Nothing else comes close."
"Legit the only resource you need. TC went from 180k -> 350k. Just memorize the top 50 for your target company and you're golden."
"PracHub Premium for one month cost me the price of two coffees a week. It landed me a $280K+ starting offer."
"Literally just signed a $600k offer. I only had 2 weeks to prep, so I focused entirely on the company-tagged lists here. If you're targeting L5+, don't overthink it."
"Coaches and bootcamp prep courses cost around $200-300 but PracHub Premium is actually less than a Netflix subscription. And it landed me a $178K offer."
"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."
"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."
"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Design An AI Playground For Very Large Prompts
Design an AI playground that lets users create, edit, run, and revisit prompts. The interviewer is especially interested in how the system handles ver...
Externally Sort a 500 GB CSV by One Column with 16 GB of RAM
This question evaluates a candidate's ability to design an external merge sort for data far larger than available memory, a core systems design skill....
Design Food Ratings and Driver Payouts
Design the backend for a food-delivery product (think DoorDash-style marketplace). The system has two distinct surfaces that you must address together...
Design Top-K, Crawler, and Chess Systems
This question evaluates system-design competency across scalable distributed services, covering real-time streaming Top-K aggregation, large-scale dis...
Design Ad Frequency and Order Tracking
This question evaluates system-design competencies for building low-latency, high-throughput ad-platform components—specifically a real-time frequency...
Design a Resilient Document Aggregation Service
This system design question tests a candidate's ability to architect a fault-tolerant, high-throughput data aggregation service involving concurrent d...
Design a Distributed Cron Job Scheduler
Design a distributed cron scheduler that creates recurring runs, dispatches work, tracks attempts, and recovers from crashes and partitions. Address d...
Design a Rental Marketplace Backend
This question evaluates a candidate's ability to design a scalable, low-latency backend for a global vacation-rental marketplace, testing competencies...
Scale a Distributed Randomized Multiset
After designing the randomized multiset on a single machine, explain how you would scale it across multiple servers. The distributed system should sup...
Design streaming error-log counting with moving average
Design a core component in a streaming system: Input: - Multiple upstream services continuously emit log events. - Each event includes at least: servi...
Review and Improve a Flawed Design Document
Review and Improve a Flawed Design Document You are given a design document for a system that has important omissions or unsafe assumptions. Review it...
Design Idempotent Due-Date and Hold Notifications
Design Idempotent Due-Date and Hold Notifications Extend a library-management system with two notification workflows: 1. A patron receives a notificat...
Design a Metrics Ingestion Pipeline
This question evaluates a candidate's ability to design a large-scale distributed system for ingesting time-series metrics at high throughput. It test...
Design a Telemetry Platform Ingesting Two Gigabytes per Second
Design a robotics telemetry platform handling two gigabytes of raw events per second. Reason through capacity, edge buffering, durable ingestion, repl...
Design Music Search, Playlists, and Playback Controls
Design the domain model and service interfaces for music search, ordered playlists, and playback controls. The discussion covers canonical catalog dat...
Design Publisher Configuration Rules
Design a supply-side advertising configuration system that manages publisher-specific rules. A publisher may own many websites, mobile apps, channels,...
Design an Ad Frequency Capping System
Design a frequency capping system for an advertising platform. A frequency cap limits how many times a user can be shown an ad, campaign, line item, o...
Design a Real-Time Online Chess Platform
Design the backend for a globally distributed real-time chess platform supporting moves, spectators, clocks, reconnects, and failover. Define authorit...
Design a Distributed Metrics Counter
This question evaluates a candidate's competency in designing scalable, highly available distributed systems for real-time telemetry ingestion and agg...
Design cart management lifecycle service
Scenario You are designing the backend for an on-demand delivery app (restaurants and grocery). Users can create a cart, modify items from multiple de...