System Design Interview Questions
Practice 968 real System Design interview questions for 2026 — System Design interview questions drawn from actual interviews with detailed solutions to power focused interview preparation. Coverage spans big tech patterns and company-specific flavors from Meta, Amazon, OpenAI, DoorDash, and Google, emphasizing software-engineering fundamentals: high-level architecture, APIs, data models, scaling strategies, and component-level tradeoffs you’ll need to codify on a whiteboard or virtual diagram tool. What’s distinctive in 2026: interviewers evaluate your ability to reason about capacity, latency, consistency, fault tolerance, and operational ownership while making measurable tradeoffs; expect more questions about AI/LLM inference pipelines, vector search and feature stores alongside classic problems like caching, sharding, messaging, and geo-distribution. Prepare by practicing clear HLD-to-LLD transitions, writing concise API contracts, doing back-of-envelope capacity math, and running timed mock interviews that force diagram clarity and follow-up handling. Focus on metrics, failure modes, and deployment/monitoring choices — those separate good answers from great ones.
"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."
"I was skeptical about the 'real questions' claim, so I put it to the test. I searched for the exact question I got grilled on at my last Meta onsite... and it was right there. Word for word."
"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 the manual review workflow
System Design: Human-in-the-Loop Review Subsystem Context You are designing a human-in-the-loop (HITL) review subsystem for a large-scale safety platf...
Design a log filtering and analytics service
Question Design a log-processing service that ingests application logs at scale and supports the following capabilities: 1. Filter logs by attributes ...
Design an online marketplace for buying and selling
System Design: Online Marketplace Backend Context Design the backend for a two-sided online marketplace where sellers list items and buyers purchase t...
Design consistent hashing for sharding
Design a Consistent-Hashing Router with Replication You are building a stateless router that maps arbitrary keys (for example, request IDs or cache ke...
Design an online ads serving system
System Design: Low-Latency Targeted Ad Serving (≤100 ms E2E) You are designing an online advertising serving system for web/app inventory with a stric...
Design scalable notification system
System Design: Low-Latency, Multi-Channel Notification Platform You are asked to design a scalable, reliable notification system that can send message...
Design flight-price search service
System Design: Cheapest Flight Search Across Multiple Providers Context Design a backend system that searches multiple flight providers (airlines, OTA...
Design collaborative document editing backend
You are asked to design the backend for a real-time collaborative document editor similar to Google Docs. The interviewer is specifically interested i...
Design a scalable news feed system
Design the backend for a social app news feed Context You are designing the backend that powers a mobile social app's home/news feed at large scale. T...
Design a scalable service and model performance
System Design: Multi-Region, 50k QPS, p95 < 100 ms Context Design an online, read-heavy key-value service (for example, a user profile or feature look...
Design a multi-level parking system
System Design: Multi‑Level Parking System Context Design the backend for a multi‑level parking facility. The system must track floors, rows, parking s...
Design a recommendation system from scratch
Recommendation System Design (two scenarios) Design a recommendation system from scratch. Cover both scenarios: 1. Location/POI recommendation: Recomm...
Design a large-scale temperature sensor system
System design: large-scale temperature sensor collection and visualization Design a system to collect and display temperature data from a very large n...
Design a distributed multi-user counter
Design a Horizontally Scalable Distributed Counter Service Context You are designing a distributed counter service used concurrently by many clients. ...
Scale crawler with thread pool
Concurrent Web Crawler — Bounded Thread Pool, Thread-Safe Frontier, Dedupe, Politeness, and Trade-offs You are refactoring an existing single-threaded...
Design cloud storage with quotas and compression
System Design: Multi‑Tenant Cloud Storage Service (Take‑Home) You are tasked with designing a multi‑tenant cloud storage service that supports file up...
Design signals across power and clock domains
Question In a SoC with two power domains A and B, design the interface for a control signal signal_1 (a registered 1-bit control such as an enable/sta...
Design resource loader and ROS-like pub/sub
System Design: Resource Loader and ROS-like Publish/Subscribe Context You are designing two foundational systems for a large-scale, real-time interact...
Design relational-to-NoSQL migration pipeline
System Design: Migrate From Relational DB to a NoSQL Key-Value Store with Snapshot + CDC Context You need to migrate data from an OLTP relational data...
Design a minimal ChatGPT with presets
System Design: Minimal ChatGPT-like Service With Reusable Presets Context Design a multi-tenant conversational AI service that supports reusable prese...