T1 · JUNIOR
Design a URL shortener (TinyURL)
bit.ly-style redirect service. Hashing, collisions, analytics.
30 min
PRACTICE BANK
Where you actually learn to design.
Tier 1 is warm-up. Tier 4 is the interview no one prepped you for. Your tutor watches every whiteboard.
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T1FoundationsWarm-up problems. Prove you can name the shapes.5 problems · 0 done
T1 · JUNIOR
Design a pastebin
Text storage with expiry, share links, blob offload.
25 min
T1 · JUNIOR
Design a rate limiter
Per-key limits under burst traffic. Token bucket, Redis atomicity.
30 min
T1 · JUNIOR
Design an in-memory key-value store
Single-node KV with TTL and eviction. Get the basics right.
35 min
T1 · JUNIOR
Design a parking-lot ticketing system
Ticketing, spot allocation, pricing. Scope it honestly.
25 min
T2CommonThe interview canon. Multi-component products at real scale.5 problems · 0 done
T2 · MID
Design a news feed (Twitter / Instagram)
Home timeline at scale. Fan-out, the celebrity problem, feed cache.
45 min
T2 · MID
Design a chat service (WhatsApp)
Delivery states, ordering, presence. Messages that never vanish.
45 min
T2 · MID
Design a notification system
Push, email, SMS fan-out with dedup and user preferences.
40 min
T2 · MID
Design a web crawler
Politeness, frontier queues, dedup at web scale.
40 min
T2 · MID
Design a link-preview & image service
Unfurl URLs safely. Async fetch, cache, image proxy.
35 min
T3AdvancedScale, consistency, and the deep dives that separate seniors.7 problems · 0 done
T3 · SENIORabove your band
Design a ride-hailing system (Uber)
Match riders to drivers in real time. Geo-index, dispatch, surge.
55 min
T3 · SENIORabove your band
Design video streaming (YouTube / Netflix)
Upload → transcode → CDN. Adaptive bitrate at planet scale.
55 min
T3 · SENIORabove your band
Design search autocomplete / typeahead
Millisecond suggestions. Prefix index, caching, ranking.
45 min
T3 · SENIORabove your band
Design a distributed cache
Build Memcached. Consistent hashing, replication, hot keys.
50 min
T3 · SENIORabove your band
Design a payment system
Move money exactly once. Idempotency, ledgers, reconciliation.
55 min
T3 · SENIORabove your band
Design Google Drive / Dropbox
File sync with chunking, delta upload, conflict handling.
50 min
T3 · SENIORabove your band
Design a ticket-booking system (Ticketmaster)
Sell each seat once under a thundering herd. Holds, isolation.
50 min
T4ExpertAmbiguous, org-scale, and adversarial. The room goes quiet.7 problems · 0 done
T4 · STAFFabove your band
Design a multi-region active-active system
Active-active across regions. Conflicts, failover, data gravity.
60 min
T4 · STAFFabove your band
Design a distributed job scheduler
Cron at platform scale. Leases, retries, exactly-once-ish.
55 min
T4 · STAFFabove your band
Design a real-time analytics pipeline
Clickstream to dashboards in seconds. Kafka, Flink, late events.
60 min
T4 · STAFFabove your band
Design an ad-serving / bidding platform
Bid, serve, and pace budgets — all inside 100 ms.
60 min
T4 · STAFFabove your band
Design a globally distributed database
Spanner-lite. Consensus, partitions, cross-ocean quorums.
60 min
T4 · STAFFabove your band
Design a platform-scale distributed rate limiter
One limiter for every service. Sharded counters, flow control.
55 min
T4 · STAFFabove your band
Critique: find the failure modes in a given design
A flawed design is on the board. Find what breaks first.
45 min