System Design Interview Questions to Practice, by Role and Level
System design interview questions grouped by role (SDE, data engineering, ML, platform, distributed systems, frontend) and level, with what each one tests.
These are the system design interview questions that come up again and again, grouped by role. For each one you will find what it tests and how long a practice round takes. Every question links to a practice page with the brief, the scale to design for, the deep-dive questions interviewers ask and the most common mistakes.
New to the format? Read how to prepare for a system design interview first, then start with the beginner questions.
Backend system design interview questions
These are the classic system design interview questions for backend, full-stack and generalist software engineers: the URL shortener, chat system, news feed, rate limiter, ticketing and payment systems that show up in interviews at product companies and big tech alike. Practice all Backend rounds.
Design a URL shortener
Build a service that turns long links into short, shareable URLs. Tests: read-heavy traffic, unique short codes, link expiration.
Beginner 35 minFreeDesign a text snippet sharing service
Create and share short text snippets with optional expiry and access controls. Tests: identifier generation, expiry and deletion, abuse prevention.
Beginner 35 min PlusDesign a comment system for social posts
Let millions of people post and read comments under popular posts and videos. Tests: separate read and write paths, queue as a write buffer, caching and eventual consistency.
Beginner 35 minFreeDesign a chat system
Create a real-time messaging experience for millions of people. Tests: websocket connections, message ordering, offline delivery.
Intermediate 45 min PlusDesign an API rate limiter
Protect a public API without slowing down well-behaved clients. Tests: token bucket, distributed counters, fail-open or closed.
Intermediate 40 min PlusDesign a notification delivery service
Deliver timely, preference-aware messages across email, push, and SMS. Tests: fan-out and prioritization, retries and deduplication, provider quotas.
Intermediate 45 minFreeDesign a search autocomplete service
Suggest useful completions quickly as users type into a search box. Tests: prefix indexing, ranking and freshness, sharding and caching.
Intermediate 40 min PlusDesign a webhook receiver service
Accept event notifications from partners like Stripe or Shopify without losing any. Tests: acknowledge after durable enqueue, signature verification, duplicates and ordering.
Intermediate 40 min PlusDesign a news feed
Deliver a relevant, fresh feed as people and publishers post. Tests: fan-out strategy, feed freshness, ranking.
Advanced 60 min PlusDesign cloud file storage
Sync large files reliably across devices and collaborators. Tests: chunked uploads, metadata and blobs, sync conflicts.
Advanced 60 min PlusDesign video streaming
Stream adaptive-quality video to a global audience. Tests: transcoding, cdn delivery, adaptive bitrate.
Advanced 60 min PlusDesign a ride-hailing service
Match riders with nearby drivers and track trips in real time. Tests: geospatial indexing, matching fairness, trip state machine.
Advanced 60 min PlusDesign a high-demand ticketing platform
Sell limited-inventory tickets fairly when a popular event goes on sale. Tests: inventory consistency, reservation expiry, sale traffic spikes.
Advanced 60 min PlusDesign a distributed web crawler
Discover and fetch public pages continuously while respecting site policies. Tests: frontier partitioning, politeness and robots rules, deduplication.
Advanced 60 min PlusDesign a collaborative document editor
Let multiple people edit and comment on the same document in real time. Tests: conflict-free editing, presence and reconnects, version history.
Advanced 60 min PlusDesign a payment processing platform
Accept payment requests reliably without charging a customer twice. Tests: idempotency keys, state transitions, reconciliation and audit.
Advanced 60 min PlusDesign a distributed task scheduler
Schedule one-off and recurring jobs across a fleet of workers. Tests: time partitioning, leases and retries, at-least-once execution.
Advanced 60 minFreeDesign a distributed caching service
Serve frequently accessed data quickly across a growing fleet of application nodes. Tests: partitioning and replication, eviction and expiry, hot keys.
Advanced 60 min PlusDesign a multi-tenant API gateway
Route external API traffic safely to independently operated backend services. Tests: control plane vs data plane, policy evaluation, safe configuration rollout.
Advanced 60 min PlusDesign a swipe-based dating app
Show nearby profiles, record swipes, and match two people who like each other. Tests: geospatial candidate search, swipe write throughput, exactly-once matches.
Advanced 60 min Plus
Data engineering system design interview questions
Data engineering interviews test whether you can move, model and trust data at scale. These rounds cover star-schema and slowly changing dimension warehouses, change data capture, real-time analytics and ad click aggregation, sessionization, IoT telemetry, log pipelines, lakehouses, reusable ETL and ELT frameworks, payments reconciliation, A/B test analytics, data quality and user data deletion. Practice all Data engineering rounds.
Design a data warehouse for an online store
Model orders, products and customers so analysts can answer sales questions quickly and correctly. Tests: fact table grain, star schema, incremental loads.
Beginner 40 minFreeDesign a customer warehouse with SCD Type 2
Keep a trustworthy history of how customer attributes change over time. Tests: business keys, effective dates, late-arriving changes.
Intermediate 45 minFreeDesign analytics for a food delivery platform
Give restaurants live order metrics and executives daily reports from one stream of order events. Tests: two consumers, two slas, streaming and batch paths, layered quality checks.
Intermediate 45 min PlusDesign a data alerting system
Notify the right owner when pipelines, data freshness, or business metrics go wrong. Tests: rule evaluation, alert grouping, escalation policy.
Intermediate 40 min PlusDesign a data quality & observability framework
Help teams detect, diagnose, and prevent incorrect or stale data. Tests: contracts and expectations, lineage, anomaly detection.
Intermediate 45 min PlusDesign a change data capture pipeline
Stream every insert, update and delete from a production database into the warehouse within minutes. Tests: log-based capture, initial snapshot and ordering, schema changes and deletes.
Intermediate 45 minFreeDesign a centralized log ingestion pipeline
Collect logs from thousands of servers so engineers can search recent logs in seconds and keep old ones for audits. Tests: agents and buffering, search index vs archive tiers, bursts and backpressure.
Intermediate 45 min PlusDesign a payments reconciliation pipeline
Match every internal payment against processor and bank settlement files, and flag what doesn't match. Tests: matching keys and tolerances, idempotent reruns, audit trail of breaks.
Intermediate 45 min PlusDesign user data deletion across a data platform
Honour right-to-be-forgotten requests across the warehouse, data lake, streams and backups within 30 days. Tests: finding every copy, deleting from immutable files, crypto-shredding and proof of deletion.
Intermediate 45 min PlusDesign a real-time analytics platform
Turn a large event stream into operational metrics people can act on. Tests: event time vs processing time, windowing, replay and deduplication.
Advanced 60 min PlusDesign a reusable ETL/ELT framework
Give many teams a consistent way to build, run, and operate data pipelines. Tests: declarative task definitions, idempotent retries, multi-tenant isolation.
Advanced 60 min PlusDesign clickstream event tracking at scale
Collect trustworthy product events from web and mobile clients. Tests: sdk batching, schema evolution, pii minimization.
Advanced 60 min PlusDesign a fraud detection data platform
Join streaming payments with historical signals for fast, explainable fraud decisions. Tests: online/offline feature parity, feature freshness, decision audit trail.
Advanced 60 min PlusDesign an ad click aggregator
Count ad clicks in near real time for advertiser dashboards, accurately enough to bill on. Tests: exactly-once counting, hot ads and skew, reconciliation with batch.
Advanced 60 min PlusDesign an IoT sensor telemetry platform
Ingest readings from millions of devices and serve live and historical views of each one. Tests: out-of-order device data, time-series storage and downsampling, hot and cold retention tiers.
Advanced 60 min PlusDesign a lakehouse for analytics and ML
Give analysts and data scientists one governed copy of company data on low-cost object storage. Tests: open table formats, small files and compaction, governance and access control.
Advanced 60 min PlusDesign video playback analytics with sessions
Turn player heartbeats into viewing sessions and quality-of-experience metrics for a streaming service. Tests: session windows, late and duplicate heartbeats, quality metrics by device and region.
Advanced 60 min PlusDesign an A/B test analytics pipeline
Compute trustworthy results for hundreds of concurrent experiments from assignment and event logs. Tests: exposure logging, metric definitions as code, sample ratio mismatch checks.
Advanced 60 min Plus
ML system design interview questions
ML system design interviews go beyond the model. These rounds ask you to design recommendation systems, feature stores, distributed training platforms, low-latency model serving, real-time fraud scoring and retrieval-augmented generation. Practice all ML & AI rounds.
Design an ML model monitoring system
Notice when a production model becomes slow, biased, or less useful. Tests: delayed ground truth, drift metrics, privacy-preserving telemetry.
Intermediate 40 min PlusDesign a recommendation system
Recommend useful content while balancing relevance, freshness, and exploration. Tests: candidate generation, ranking, cold start.
Advanced 60 minFreeDesign a feature store
Serve consistent ML features for both training jobs and online predictions. Tests: point-in-time correctness, offline/online parity, backfills.
Advanced 60 min PlusDesign a distributed model training platform
Schedule reproducible training jobs across shared compute and data. Tests: resource scheduling, checkpointing, experiment lineage.
Advanced 60 min PlusDesign a low-latency ML model serving platform
Deploy models safely and handle variable inference traffic. Tests: batching, autoscaling, canary rollout.
Advanced 60 min PlusDesign a retrieval-augmented generation system
Answer questions from a changing document collection with traceable sources. Tests: chunking and embedding, hybrid retrieval, grounding and access control.
Advanced 60 min PlusDesign real-time fraud scoring
Score transactions in milliseconds and route uncertain cases for review. Tests: feature freshness, fallback policy, human review loop.
Advanced 60 min Plus
Platform and infrastructure system design interview questions
Platform, SRE and infrastructure interviews focus on the systems other engineers depend on. These rounds cover internal developer platforms, multi-region failover, service discovery, deployment pipelines, configuration and secrets management, and observability. Practice all Platform rounds.
Design service discovery for a growing fleet
Let services find healthy endpoints as instances scale and move. Tests: health checks, caching and ttl, control-plane availability.
Intermediate 40 min PlusDesign a safe deployment platform
Roll out changes across hundreds of services with fast, safe rollback. Tests: canary analysis, artifact provenance, rollback safety.
Intermediate 45 min PlusDesign an internal developer platform
Help product teams ship services without rebuilding infrastructure each time. Tests: golden paths, self-service apis, escape hatches.
Advanced 60 minFreeDesign a multi-region failover strategy
Keep a customer-facing service available through a regional outage. Tests: rto and rpo, replication lag, failover testing.
Advanced 60 min PlusDesign a secrets management platform
Distribute and rotate credentials safely across services and environments. Tests: identity-based access, rotation workflow, audit and revocation.
Advanced 60 min PlusDesign a metrics and observability platform
Collect useful signals from services without making telemetry unbounded. Tests: cardinality control, retention tiers, alert routing.
Advanced 60 min PlusDesign a configuration control plane
Deliver safe, auditable configuration changes to a large service fleet. Tests: push vs pull, validation and rollout, last-known-good state.
Advanced 60 min Plus
Distributed systems design interview questions
Distributed systems rounds test the building blocks underneath every large system: replication, partitioning, consensus, ordering and coordination. Design a distributed key-value store, a unique ID generator, a message queue, a lock service and a geo-replicated database. Practice all Distributed systems rounds.
Design a unique ID generator
Issue unique, roughly sortable IDs at high rate across data centers. Tests: snowflake-style layout, clock skew, worker id assignment.
Beginner 30 min PlusDesign a distributed key-value store
Store and serve keys across many nodes with tunable consistency. Tests: consistent hashing, quorum reads and writes, conflict resolution.
Advanced 60 minFreeDesign a distributed message queue
Build a durable, partitioned log that producers and consumers can rely on. Tests: partitions and ordering, replication and isr, consumer offsets.
Advanced 60 min PlusDesign a distributed lock service
Let services coordinate exclusive access without deadlocks or split brain. Tests: leases and fencing tokens, consensus backing store, client failure detection.
Advanced 60 min PlusDesign leader election for a service cluster
Keep exactly one active coordinator while nodes come and go. Tests: raft-style terms, heartbeats and timeouts, split-brain prevention.
Advanced 60 min PlusDesign a geo-replicated database
Serve reads and writes from several regions with clear consistency trade-offs. Tests: single vs multi-leader, conflict resolution, cross-region latency.
Advanced 60 min Plus
Frontend and mobile system design interview questions
Frontend and mobile system design interviews focus on the client: state management, data fetching and caching, offline behaviour, rendering performance and safe releases. These rounds cover offline-first mobile sync, image-heavy feeds, a collaborative whiteboard client, micro-frontend platforms, and release and feature-flag systems. Practice all Frontend & mobile rounds.
Design mobile release and feature flags
Ship app changes safely when users update on their own schedule. Tests: remote config, staged rollout, api versioning.
Beginner 35 min PlusDesign offline-first mobile sync
Let a notes app work offline and merge cleanly when it reconnects. Tests: local database, change log and cursors, conflict resolution.
Intermediate 45 minFreeDesign an image-heavy feed client
Keep an infinite photo feed smooth on slow networks and older phones. Tests: list virtualization, image cdn and sizes, caching and prefetch.
Intermediate 40 min PlusDesign a collaborative whiteboard client
Let many people draw on one canvas in real time without conflicts. Tests: crdts vs ot, rendering pipeline, presence and reconnection.
Advanced 60 min PlusDesign a micro-frontend platform
Let many teams ship parts of one web app independently. Tests: composition strategy, shared dependencies, isolation and fallbacks.
Advanced 60 min Plus