System Design
Draw systems, estimate capacity and test the trade-offs.
Projects, case studies and mock exams
Build a complete shortener from scope to failure handling.
6 steps · 35 minProject · IntermediateA news feedBuild a feed that handles both ordinary members and a large broadcaster.
7 steps · 40 minProject · IntermediateA chat appBuild a durable chat path that survives retries and reconnects.
7 steps · 40 minCase study · IntermediateNearby driversKeep nearby-driver queries fresh across cell boundaries and delayed updates.
6 steps · 30 minCase study · IntermediateReliable notificationsKeep a stable identity across scheduling, delivery and provider reconciliation.
6 steps · 30 minCase study · AdvancedPaymentsReconcile ambiguous payment outcomes under one durable intent.
6 steps · 35 minCase study · AdvancedTicket salesProtect a hot seat while bounding launch traffic and late-payment effects.
6 steps · 35 minCase study · AdvancedVideo streamingDeliver complete video renditions while making retries and cold traffic safe.
6 steps · 35 minProject · AdvancedA web crawlerBuild a polite crawler with durable scheduling and duplicate-safe output.
7 steps · 45 minMock exam · AdvancedTimed mock: document exportsComplete a timed export-service design with checked stages and failure handling.
6 questions · 35 minProject · ExpertA clickstream pipelineBuild a replayable event pipeline with deduplication and corrected session metrics.
7 steps · 28 minCase study · ExpertRide app analyticsRecommend a city operating measure with corrected event time and a defensible denominator.
6 steps · 24 minCase study · ExpertA live dashboardDesign a dashboard that distinguishes processing delay from absent business events.
6 steps · 24 minCase study · ExpertAn experiment platformBuild stable assignments and distinguish a business result from a broken experiment.
6 steps · 24 minMock exam · ExpertTimed mock: telemetry platformComplete seven timed design stages with a retained-input and recovery contract.
7 questions · 35 minBuild a design from requirements to failure handling. You work on an editable board with request paths, storage, caches, queues and data pipelines. Each task checks the result and explains the missing requirement. Start with estimates and interfaces, then practice replication, partitioning and asynchronous work. Guided projects turn the parts into a URL shortener, a news feed and a chat service. Case studies examine payments, hot inventory and analytics. The data systems sequence covers streaming, warehouse models, change data capture and backfills. Finish with interview questions and timed mock designs. Every scenario uses fictional organizations and workloads.
Interview practice
Explain what you've learned in a full-screen interview. Speak or type, then review your answers against the rubric for your level.
Interview loops by jobBeginner
Requirements and estimates
Agree on scope and quantify the workload before choosing components.
Request paths and storage
Connect clients, replicas, data stores and caches to a concrete access pattern.
Interfaces and a first design
Define APIs and identity, then build a complete URL shortener.
Intermediate
Distributed state
Choose replication, partitioning and cache policies around freshness and hot-key failures.
Asynchronous work
Build durable jobs, bounded admission and identifiers that survive retries and clock changes.
Application delivery
Design public content, search, feeds, chat, location matching and notifications.
Advanced
Distributed correctness
Define consistency contracts and recover sagas and replayed streams without losing intent.
Reliable operations
Measure user objectives, fence regional writers and reconcile uncertain payment outcomes.
Design under pressure
Design hot inventory, streaming video and a polite crawler, then practice interview and timed assessment work.
Expert
Data pipelines
Choose processing paths, model fact grain, and build a corrected clickstream pipeline.
Storage and recovery
Capture committed changes, publish table snapshots, and recover results without duplication.
Analytics decisions
Define comparable metrics, design decision systems, and complete timed data engineering interviews.