SYSTEM DESIGN · FOUNDATIONS → ARCHITECT

Design like the level above you.

45 units · 24 case studies · a tutor that watches your whiteboard.

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YOUR MIXtuned for Mid · shifts with persona

Read half. Design half.

50%read, watch, grok·50%design, critique, defend
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PRACTICE BANK24 case studies · unlocked to Tier 2 for Mid
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T1 · JUNIOR

Design a URL shortener (TinyURL)

bit.ly-style redirect service. Hashing, collisions, analytics.

#estimation#indexing#caching
30 min
T1 · JUNIOR

Design a pastebin

Text storage with expiry, share links, blob offload.

#object-storage#api-design#caching
25 min
T1 · JUNIOR

Design a rate limiter

Per-key limits under burst traffic. Token bucket, Redis atomicity.

#rate-limiting#token-bucket#redis
30 min
T1 · JUNIOR

Design an in-memory key-value store

Single-node KV with TTL and eviction. Get the basics right.

#in-memory-store#eviction#replication
35 min
T1 · JUNIOR

Design a parking-lot ticketing system

Ticketing, spot allocation, pricing. Scope it honestly.

#schema-design#functional-requirements#api-design
25 min
T2 · MID

Design a news feed (Twitter / Instagram)

Home timeline at scale. Fan-out, the celebrity problem, feed cache.

#fanout#caching#sharding
45 min
T2 · MID

Design a chat service (WhatsApp)

Delivery states, ordering, presence. Messages that never vanish.

#message-queues#pub-sub#consistency-models
45 min
T2 · MID

Design a notification system

Push, email, SMS fan-out with dedup and user preferences.

#message-queues#fanout#idempotency
40 min
T2 · MID

Design a web crawler

Politeness, frontier queues, dedup at web scale.

#message-queues#dedup#backpressure
40 min
T2 · MID

Design a link-preview & image service

Unfurl URLs safely. Async fetch, cache, image proxy.

#object-storage#cdn#caching
35 min
T3 · SENIORabove your band

Design a ride-hailing system (Uber)

Match riders to drivers in real time. Geo-index, dispatch, surge.

#geospatial-index#consistent-hashing#pub-sub
55 min
T3 · SENIORabove your band

Design video streaming (YouTube / Netflix)

Upload → transcode → CDN. Adaptive bitrate at planet scale.

#cdn#object-storage#estimation
55 min
T3 · SENIORabove your band

Design search autocomplete / typeahead

Millisecond suggestions. Prefix index, caching, ranking.

#full-text-search#caching#sharding
45 min
T3 · SENIORabove your band

Design a distributed cache

Build Memcached. Consistent hashing, replication, hot keys.

#consistent-hashing#eviction#replication
50 min
T3 · SENIORabove your band

Design a payment system

Move money exactly once. Idempotency, ledgers, reconciliation.

#idempotency#distributed-transactions#sagas
55 min
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