HLD
Design a Rate Limiter
A rate limiter throttles the number of requests a client, user, or IP can send to a service within a time window, protecting backend systems from abuse and accidental overload.
StripeUberAmazonGoogle+2
Top 23 System Design Interview Questions
23 hand-picked high-level and low-level system design questions, each with a real description, expected key points, and the concepts it teaches.
By DevsUnite · 23 Questions
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HLD
Design TinyURL
TinyURL converts long URLs into short, unique aliases that redirect back to the original when visited. The core design challenge isn't storage. It's generating short keys that never collide, at scale.
AmazonGoogleMicrosoftMeta+2
HLD
Design Twitter
Twitter is a social platform for posting short messages (tweets) and following other users to see their posts in a personalized, roughly-chronological timeline.
MetaTwitter/XUberMicrosoft+2
HLD
Design YouTube
YouTube lets users upload, store, and stream video at massive scale to a global audience on wildly varying network conditions and devices. The hard parts are ingestion and delivery.
GoogleNetflixAmazonMeta+2
HLD
Design Google Drive
Google Drive stores files in the cloud, syncs them across a user's devices, and supports sharing and collaboration. The core design challenges are efficient sync and conflict resolution.
GoogleDropboxMicrosoftAmazon+2
HLD
Design Google Maps
Google Maps provides map rendering, location search, and turn-by-turn routing across a global road network, updated with live traffic.
GoogleUberGrabApple+2
HLD
Design a Key-Value Store
A distributed key-value store (like DynamoDB or Cassandra) provides simple get/put access to data but must remain available and performant across many machines and failures.
AmazonGoogleMicrosoftUber+2
HLD
Design a Distributed Message Queue
A message queue (like Kafka or RabbitMQ) decouples producers and consumers of data, letting services communicate asynchronously and absorb bursts without dropping work.
AmazonLinkedInUberConfluent+2
HLD
Design a News Feed System
A news feed aggregates and ranks content from many sources a user follows into a single, personalized, scrollable stream. Beyond the fan-out problem sits the ranking problem.
MetaLinkedInTwitter/XInstagram+2
HLD
Design Google Docs
Google Docs is a cloud-based word processor supporting real-time multi-user editing, where every collaborator sees others' changes almost instantly without clobbering each other.
GoogleAtlassianMicrosoftNotion+2
HLD
Design ChatGPT System
Designing a system like ChatGPT means serving large language model inference to millions of users with acceptable latency and cost, not training the model itself.
OpenAIMicrosoftGoogleMeta+2
HLD
Design Netflix
Netflix streams a large catalog of video on demand to a global audience, with personalized recommendations and playback that adapts to each viewer's connection.
NetflixAmazonDisney+Google+2
HLD
Design Reddit
Reddit organizes discussion into communities with threaded comments and vote-driven ranking, where the hot ranking must stay fresh without recomputing everything constantly.
RedditMetaTwitter/XDiscord+2
HLD
Design Uber
Uber matches riders with nearby drivers in real time, tracks trips as they happen, and handles pricing, all while drivers and riders move continuously.
UberLyftGrabOla+2
HLD
Design WhatsApp
WhatsApp delivers one-to-one and group messages reliably and in order, with delivery receipts, offline queuing, and end-to-end encryption.
MetaSignalTelegramGoogle+2
HLD
Design Instagram
Instagram is a photo and video sharing platform with a personalized feed, stories, and a heavy read-to-write ratio dominated by media delivery.
MetaSnapTikTokPinterest+2
LLD
Design a Notification System
A notification system delivers messages across push, SMS, and email channels reliably, respecting user preferences and avoiding duplicate or unwanted sends.
AmazonGoogleMetaTwilio+2
HLD
Design a Payment System
A payment system moves money between parties correctly and exactly once, reconciling with external processors that can fail or respond slowly.
StripePayPalAmazonRazorpay+2
LLD
Design Tic-Tac-Toe / Chess
Model a turn-based board game with players, moves, win detection, and a rules engine that extends from tic-tac-toe to chess without restructuring.
AmazonGoogleMicrosoftMeta+2
HLD
Design TikTok
TikTok serves an endless personalized short-video feed, where the recommendation engine matters more than the social graph and every scroll must feel instant.
TikTokMetaGoogleSnap+2
LLD
Design a Food Delivery App
Model an online food ordering and delivery system like Zomato or Swiggy: restaurants, menus, carts, order lifecycle, and delivery partner assignment.
ZomatoSwiggyUberDoorDash+2
LLD
Design a Music Streaming Service
Model a service like Spotify: a catalog of songs and albums, user playlists, playback queue, and a recommendation hook — a classic machine-coding round.
SpotifyAppleAmazonGoogle+2
LLD
Design a Dating App
Model a dating app like Tinder: user profiles, preference-based discovery, the swipe interaction, mutual-match detection, and chat unlocked on match.
TinderBumbleHingeMeta+2
Frequently asked questions
What is the System Design Sheet?
A curated set of high-level (HLD) and low-level (LLD) system design interview questions, designing systems like a rate limiter, TinyURL, and Twitter, each with a real description of the problem, the key points a strong answer should cover, the concepts it teaches, the companies known to ask it, and a reference article and video.
How many questions does it have?
23 questions, a mix of high-level (18) and low-level (5) design problems, each paired with a reference article and video.
Is it free to use?
Yes. Browsing every problem on this page is completely free, with no account required. Creating a free DevsUnite account lets you save your checked-off progress, star favorites, and add personal notes that sync across devices.
Do I need an account to track my progress?
You can read and solve every problem without logging in. An account is only required to mark a problem as done, star it, or add a note. Those actions save to your account instead of resetting on refresh.