+9Design a rate limiterSystem designDesign a service that limits how many requests each API client can make. It sits in front of every API endpoint at high traffic.
Reported by 1 member · Last asked Oct 2026
Questions
- +9
Design a sandboxed cloud IDESystem designGive every user a browser-based editor with a terminal and a private container that runs their code, starts in seconds, isolates untrusted code, and saves their work.Last asked Oct 2026- +7Design a distributed web crawlerSystem designCrawl billions of web pages politely and repeatedly, deduplicating URLs and content, to feed a search index or a training-data pipeline.Last asked Oct 2026
- Design a real-time trivia battle royale with live spectatorsSystem designDesign a trivia battle royale. A room holds dozens to a hundred or more players. Questions go out round by round; after each round, players who answered wrong and the slowest…Last asked Oct 2026
- Design a real-time multiplayer typing raceSystem designDesign an online typing race. Each race has 2 to 8 players. When the race starts, every player gets the same generated passage and types it; the first to finish the whole passage…Last asked Oct 2026
Check and insert among a million user IDsSystem designA service holds about a million user IDs. Each request carries a user ID: if it is not in the set yet, add it. Decide how to store the IDs and run this check-and-insert, and talk…Last asked Oct 2026- +5Design a payment systemSystem designAccept card payments for merchants: authorize, capture, settle with card networks, and reconcile, never charging twice or losing money.Last asked Oct 2026
One-on-one chat system with presence and offline queueSystem designDesign direct messaging for single-device users: delivery, presence, offline-recipient queueing, session storage, and the choice of message bus. Group chat is explicitly out of…Last asked Oct 2026- +1Design a feature flag serviceSystem designLet teams turn features on for a percentage of users or specific accounts, with changes reaching every service within seconds and no per-request network call.Last asked Oct 2026
+6Design a metrics monitoring systemSystem designCollect metrics from every host and service, store them as time series, power dashboards over months of data, and alert when thresholds are crossed.Last asked Oct 2026
Design a lab machine fleet monitor with remote rebootSystem designDesign a service that watches a fleet of lab machines running compute workloads. Each machine polls the service for work; a work item names a payload the machine must download…Last asked Sep 2026
+8Design typeahead suggestionsSystem designSuggest completions as the user types into a search box, within tens of milliseconds, ranked by popularity and fresh with trending queries.Last asked Sep 2026
Design the data flow behind a food delivery restaurant listSystem designWhen a customer opens a food delivery app with a delivery address, the home screen lists the restaurants that can deliver there. Design how restaurant data travels from the…Last asked Sep 2026- Design a distributed power grid control systemSystem designMonitor and control generators, substations and loads across a power grid, reacting to failures and demand changes in seconds, safely, even when parts of the network are cut off.Last asked Sep 2026
- Design a workflow orchestration systemSystem designUsers define a workflow as steps with dependencies, then start runs of it. Design the system that runs each step once its dependencies finish, records the state of every run and…Last asked Sep 2026
Design a Terraform provider for a cloud resourceSystem designYou work on infrastructure at a cloud provider. Customers want to manage one of your resources with Terraform: declare it in config, apply it, change it later and destroy it the…Last asked Sep 2026- +4Design an online chess gameSystem designMatch players of similar rating, play live games with clocks, handle disconnects and reconnects, and keep game history and ratings.Last asked Sep 2026
Load daily LLM chat logs into a warehouse idempotentlySystem designEvery day one JSONL file of LLM conversations lands in object storage; each line is a conversation with an id, a user id, its messages and metadata. Design the job that loads it…Last asked Sep 2026- Design a real-time comment feed with optimistic updatesSystem designDesign the front end of a comment section where other people's comments arrive live and the viewer can post their own. The focus is optimistic posting: a submitted comment shows…Last asked Sep 2026
- +3Design a CI/CD systemSystem designOn every commit, build and test the code on a fleet of workers, then roll it out to production safely, with logs, retries and rollbacks.Last asked Sep 2026
- Cut read latency in an existing relational database designSystem designYou are shown the database design behind a real service: a relational store that has become slow to read. Propose how you would change it to bring read latency down. Start by…Last asked Sep 2026
- +2Design an image sharing service that stores each file onceSystem designDesign a service where users upload, view, download and delete images, and identical images are stored only once, keyed by a content hash. Explain how metadata and blobs stay…Last asked Sep 2026
Coordinate a fleet of restaurant robotsSystem designDesign the system that coordinates many robots working in a restaurant. Start by pinning down what work the robots do, then cover how tasks are assigned, how execution state is…Last asked Sep 2026- Design a Kafka-based file watcher for millions of filesSystem designDesign a file watcher that tracks millions of files and publishes change events to downstream consumers through Kafka. Cover the first full discovery of files, ongoing changes…Last asked Sep 2026
- +7Design a Slack-like chat systemSystem designWorkspaces, channels, threads and direct messages with real-time delivery, unread state, search and history, for large companies.Last asked Sep 2026
- Design a digital game store like SteamSystem designDesign a digital game distribution platform like Steam. Players use a desktop client to browse a store, buy games, see what they own in a library, and download, install and update…Last asked Sep 2026
- Design a telemetry pipeline that reconciles inconsistent metric namesSystem designA large fleet of client software already in the field sends telemetry to a data infrastructure team. Each record carries a telemetryname saying what it measures (a request…Last asked Sep 2026
Design a Supercharger backend: billing, stall telemetry and finding a free chargerSystem designDesign the backend for a network of EV fast-charging sites, each with several stalls. Three requirements: 1. Billing: measure the energy delivered in every charging session and…Last asked Sep 2026
Design an autonomous-vehicle camera and perception pipelineSystem designDesign the path from a self-driving car's cameras to its perception outputs: capture, synchronization and timestamps across cameras, image processing, model inference on the…Last asked Sep 2026
+4Design Google DocsSystem designMany people edit the same document at once and see each other's changes and cursors live, with offline edits and full version history.Last asked Sep 2026- +5Design Facebook MessengerSystem designOne-to-one and group messaging for a billion users: real-time delivery, offline sync, read receipts and message history on every device.Last asked Sep 2026
Design a control plane for cloud clusters with host health checksSystem designDesign the management layer of a cloud platform that runs clusters of hosts (VMs or physical machines). It takes requests to create, resize and change clusters, decides which…Last asked Sep 2026
+4Design a notification systemSystem designA shared service other teams call to send push, email and SMS notifications: templates, user preferences, retries, deduplication and rate limits.Last asked Sep 2026- Design Instagram StoriesSystem designDesign the stories feature of a photo and video app: users post photos or short videos that their followers can view for 24 hours, after which they disappear. At the top of the…Last asked Sep 2026
- Design a people-you-may-know friend recommendation systemSystem designDesign the "people you may know" feature of a large social network: each user sees people they are not connected to yet but probably know, and can send a friend request or dismiss…Last asked Sep 2026
- Design a distribution-center inventory update serviceSystem designDistribution centers send stock updates. Design the service that keeps the latest quantity, availability and last-update time for every location and item pair and answers lookups…Last asked Sep 2026
- +1Critique a design doc from the team's backlogSystem designThe interviewer hands over a real design doc and asks for a critique: surface risks, propose alternatives, and say what is missing before this could ship.Last asked Sep 2026
Design a book price aggregatorSystem designShow the current price of a book across many online sellers, keeping prices fresh while respecting each seller's API limits.Last asked Sep 2026- Design a single-node in-memory cache with a write-ahead logSystem designDesign an in-memory key-value cache that sits inside one web service. Then make it survive restarts with a write-ahead log, and explain how you would shard it and cut lock…Last asked Sep 2026
- Design the metadata service of a strongly consistent distributed file systemSystem designDesign the namespace layer for a distributed file system: make directories, list them, put and get files, delete, and walk the tree recursively. A listing must reflect every write…Last asked Sep 2026
Design a matchmaking service for an online gameSystem designDesign a matchmaking service. It must let players join the queue and cancel, match two compatible players, notify both when a match is found, and deal with disconnects and…Last asked Sep 2026- Design a global caching service for small imagesSystem designDesign a global caching service for small images, backed by a single database that holds every image and is the source of truth. Cover the read path, the update path, the cache…Last asked Sep 2026
- Design simulation infrastructure to evaluate a self-driving model on limited computeSystem designStart from an open question: how would you evaluate a self-driving model? Then design the infrastructure: running thousands of simulations when there is not enough compute…Last asked Sep 2026
- Latency got worse right after a deploy: what do you do?System designA new version went out and 10 to 15 minutes later latency or reliability is degrading. Explain how you would notice, how you decide whether to roll back right away or investigate…Last asked Sep 2026
- Design a global one-to-one voice calling systemSystem designDesign voice calls between registered mobile users worldwide, at millions of users. A caller rings another user, the callee gets an incoming-call notification and accepts or…Last asked Sep 2026
- +5Design an S3-like object storage systemSystem designStore trillions of objects of any size with eleven nines of durability, and serve reads and writes over an HTTP API at high throughput.Last asked Sep 2026
- Design a distributed file system for large structured datasetsSystem designDesign a distributed file system or storage service for large structured datasets that data-processing jobs read and write. Go past the box diagram and walk through the concrete…Last asked Sep 2026
- Data platform with ingestion and governed accessSystem designDesign a system that ingests large-scale data, processes it, and serves stakeholders with different access needs and sensitivities.Last asked Sep 2026
- Design distributed storage for build artifactsSystem designDesign a storage system for build artifacts: binaries, packages and archives produced by the build pipeline that later stages download to test and deploy. Cover the upload and…Last asked Sep 2026
- From a monorepo commit to an over-the-air vehicle updateSystem designAn engineer commits a change to the company's monorepo. Some time later, software containing that change is running on customers' cars. Describe the whole path in between: build…Last asked Sep 2026
- Design an offline-first client that syncs edits across devicesSystem designDesign the client side of an app in which users edit data over an unreliable network. Every edit is saved to local storage on the device as it is made, and the user keeps working…Last asked Sep 2026
- +3Design a nearby points-of-interest serviceSystem designGiven a user's location, return the closest restaurants, shops and other places of interest within a radius, fast, for a read-heavy global audience.Last asked Sep 2026
- Design an OS notification platform, working with an AI assistantSystem designDesign the notification system of a desktop operating system: the platform piece that lets many applications raise notifications and shows them to the user. Cover the app-facing…Last asked Sep 2026
- +6Design TinyURLSystem designTurn long URLs into short links and redirect visitors fast, at billions of redirects a day, with optional custom aliases and expiry.Last asked Sep 2026
- +3Design UberSystem designRiders request trips, nearby drivers get matched, and both see live location until drop-off, with pricing and payment, for millions of trips a day.Last asked Sep 2026
- +1Design an online game leaderboardSystem designShow the top players and each player's own rank in real time as millions of scores update.Last asked Sep 2026
- Design a content delivery networkSystem designDesign a CDN that serves static content from servers close to users. Cover how a request reaches the nearest edge, what the edge caches and for how long, cache misses and the path…Last asked Sep 2026
Model cumulative booking metrics and first and last booking timesSystem designA data engineering round: design the tables and pipeline that report cumulative booking metrics over time, along with each user's (or listing's) first and last booking time. Cover…Last asked Sep 2026- +12Design a distributed job schedulerSystem designDesign a service that runs millions of scheduled and on-demand jobs (cron-like and one-off) reliably across a fleet of workers.Last asked Sep 2026
Design a real-time 3D playback system for recorded vehicle logsSystem designDesign a system that replays a recorded vehicle drive as an interactive 3D scene. A drive is a set of timestamped logs (sensor data, vehicle pose and similar) kept in object…Last asked Sep 2026
Document store with drive sync and org ACLsSystem designDesign a Drive-like document store with upload and download, large-file handling and organization-level access control; real-time multi-device sync is out of scope. Reported on…Last asked Sep 2026
+7Design a top-K popular items systemSystem designReport the K most viewed or played items over sliding windows (last minute, hour, day) from a firehose of billions of events per day.Last asked Aug 2026
Aggregate and query vehicle telemetrySystem designA fleet of vehicles reports data such as detected obstacles and vehicle metrics. Design how this data is ingested, aggregated and queried, for example counts over time and place…Last asked Aug 2026- Fast search over large autonomous-vehicle logsSystem designVehicles produce large raw logs and vehicle records. Design how engineers search them quickly, for example for every record that matches some conditions, when the data is far…Last asked Aug 2026
- Design an autonomous-vehicle simulatorSystem designDesign a simulation system for testing self-driving software: how scenarios are defined, how the vehicle software runs against simulated sensors and other actors, how many…Last asked Aug 2026
- Schedule video processing across CPU and GPU workersSystem designVideo processing jobs have stages, some suited to CPUs and some to GPUs. Design how jobs are split into stages and scheduled across the two pools of machines to keep both busy…Last asked Aug 2026
- Design a project-to-contractor matching systemSystem designDesign a system that matches projects needing work done with contractors who can do it: how projects and contractor profiles are stored and indexed, how candidates are found and…Last asked Aug 2026
- Design a payments ledgerSystem designDesign the double-entry ledger behind a payments API: money movements must never be lost or applied twice.Last asked Aug 2026
- Count keywords across a fleet's logsSystem designMany machines write logs, and you need a distributed system that gathers those logs and counts how often given keywords appear in them. The keyword set, log volume and freshness…Last asked Aug 2026
- +4Design a distributed rate limiterSystem designDesign a rate limiter that enforces a token-bucket limit per client across a fleet of servers. Cover where the limiter sits, where the bucket state lives (a shared store, local…Last asked Aug 2026
- +6Design YouTubeSystem designUpload videos, transcode them into many formats, and stream them worldwide with adaptive bitrate, along with views, likes and comments.Last asked Aug 2026
- Design an order fulfillment systemSystem designDesign the system that takes a customer's order through to delivery, in the style of a large online retailer: inventory reservation, choosing the warehouse, picking and packing…Last asked Aug 2026
- Design an interactive query notebookSystem designDesign a notebook product where users write queries in cells, run them interactively against a data warehouse, and see results stream back into the notebook. Cover the session…Last asked Aug 2026
- Design a product image upload pipeline for sellersSystem designDesign the pipeline sellers use to upload product images: accepting the upload, processing the images, storing them, and serving them on product pages.Last asked Aug 2026
- Design faceted product searchSystem designDesign product search for a large catalog where shoppers narrow results with facets (filters on product attributes) and see how many results each filter value has. Cover indexing…Last asked Aug 2026
Design an ad frequency capping serviceSystem designDesign the service that decides, at ad-serving time, whether a user may see another ad from a campaign, so that caps like "at most 3 per user per day" or "exactly once" hold…Last asked Aug 2026- Design an idempotent double-entry ledger serviceSystem designDesign a ledger service that records money movements for merchants as double-entry transactions and answers balance and history queries. Cover the data model, making writes…Last asked Aug 2026
- Design an incident ticket correlation platformSystem designDesign a platform that takes in a high volume of incident tickets and alerts at the same time and groups the ones caused by the same underlying problem, so responders see one…Last asked Aug 2026
- +5Design an ad click aggregation systemSystem designCount ad clicks per ad and per time window from billions of events a day, accurately enough to bill advertisers, with results available within minutes.Last asked Aug 2026
- Design a distributed crossword solverSystem designGiven a large crossword grid with about a hundred slots and a dictionary of around a million words, design a service that fills the grid. One machine cannot search the space fast…Last asked Aug 2026
Design real-time comments on a design canvasSystem designLet people pin comments to points and objects on a shared design canvas, reply in threads, and see each other's comments live as the design changes underneath them.Last asked Aug 2026- Design reliable command delivery between autonomous vehicles and the cloudSystem designDesign how commands are sent between the cloud and a fleet of autonomous vehicles (and acknowledgements back), so a command is delivered and acted on exactly as intended even with…Last asked Aug 2026
- Order service whose database write succeeds but queue publish failsSystem designDesign the order path of an online bookstore. When an order request arrives, the service inserts the order into its database and then publishes a message to a queue (Amazon SQS)…Last asked Aug 2026
- Design cloud photo storage with sync across devicesSystem designDesign a photo library in the cloud that keeps every one of a user's devices in sync: upload new photos from a phone, see them on the other devices, and propagate edits and…Last asked Aug 2026
- Design search over user posts with boolean queriesSystem designDesign search over users' status posts on a large social network. Queries combine words with AND and OR (for example cats AND (dogs OR birds)), and new posts should become…Last asked Aug 2026
- Design trackable product links that reward every Nth visitorSystem designCompanies create and edit product pages with images and descriptions, generate unique links to share on social media, and see each link's reach and engagement. The platform also…Last asked Aug 2026
- Design a shared-ride matching serviceSystem designDesign the service that matches riders into shared rides and runs those trips: taking requests, deciding which riders share a vehicle, planning pickups and drop-offs along the…Last asked Aug 2026
- Model the data for an ad campaign management systemSystem designDesign the schema behind the advertiser side of an ads business: advertisers, campaigns, ad groups, creatives, targeting, budgets and orders, plus how impressions and spend are…Last asked Aug 2026
- Design log storage with live tailing of growing filesSystem designProducers keep appending records to log files at very high volume. Store them durably and let users read files back, including users who read a file while it is still being…Last asked Aug 2026
- Design an online tic-tac-toe service over REST, with matchmakingSystem designTwo players are matched online and play tic-tac-toe from their own devices. Clients may only talk to the server through REST APIs, and the service runs in several regions. Design…Last asked Aug 2026
- +5Design a logging serviceSystem designIngest logs from every service at terabytes per day, make them searchable within seconds, and keep them cheaply for months.Last asked Aug 2026
- Design calendar front-end state for recurring eventsSystem designDesign the client-side state for a calendar app that supports recurring events. Cover how recurrence rules are stored versus expanded into visible occurrences, how a single…Last asked Aug 2026
- Design a reliable job schedulerSystem designDesign a service that runs jobs at scheduled times at large scale, such as payment jobs that must run on time and exactly once in effect. Cover storing schedules, finding jobs…Last asked Aug 2026
- Design a token-based rate limiter for AI agentsSystem designAI agents call paid services, and each call spends billing tokens. Design a limiter that caps how many tokens each agent or customer can spend over time, enforces the cap across…Last asked Aug 2026
- Design a collaboratively edited playlistSystem designSeveral people add, remove and reorder songs in the same playlist at once. Scale is not the point: model the ordered list so reorders are cheap and concurrent edits resolve…Last asked Jul 2026
- Model access permissions in a graph database and migrate to itSystem designDesign how to store which users can access which resources in a graph database, and how to answer access questions from it. The data lives in an existing database today, so the…Last asked Jul 2026
- Design customer support with handoff from virtual agent to humanSystem designUsers chat with a virtual agent and can be escalated to a human support agent. Design the system with the focus on the handoff: how the conversation's context goes with it, who…Last asked Jul 2026
- Design a personalized weekly deals serviceSystem designEvery week each user gets a set of deals picked for them. Design how deals are collected, matched to each user, stored and delivered, and how the weekly run stays on time as users…Last asked Jul 2026
Design a notes app that syncs across devicesSystem designDesign a notebook app whose notes stay in sync across a user's devices. Cover the data model, how changes made offline are sent and merged, how conflicting edits are resolved, and…Last asked Jul 2026- Design in-flight entertainment for a small seat screenSystem designDesign the entertainment system on an airplane seat's small screen: what passengers can browse and watch, and the system behind it on the aircraft. Cover the interface for a small…Last asked Jul 2026