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System Design

The building-block techniques — and how real companies combine them at scale. · 38 topics · 13 live

Core Techniques
Load Balancing→
Route requests across servers by strategy.
Caching & LRU→
Hits, misses, and least-recently-used eviction.
Rate Limiting→
Token bucket absorbs bursts, then throttles.
Sharding & Consistent Hashing→
Spread data across nodes on a hash ring.
Replication→
Leader / follower, failover, read replicas.
Message Queues→
Producers, consumers, backpressure.
CDN & Edge→
Serve content from the nearest location.
Architectures · Social & Feeds
News Feed (Twitter)→
Home timelines — fan-out on write vs read.
Instagram→
Photo upload, media pipeline, and feed.
FacebookSoon
Social graph, feed, and notifications.
RedditSoon
Communities, voting, hot ranking.
TikTokSoon
Short-video feed and recommendation.
Architectures · Messaging & Real-Time
Chat (WhatsApp)→
Erlang/OTP — real-time, store-and-forward, E2EE.
S
SlackSoon
Channels, threads, real-time sync.
DiscordSoon
Voice + chat, massive guilds.
ZoomSoon
Low-latency video conferencing (SFU).
Live CommentsSoon
Real-time comment fan-out at scale.
Architectures · Media & Streaming
SpotifySoon
Audio streaming, CDN, recommendations.
TwitchSoon
Live video ingest and distribution.
Architectures · Commerce & Payments
A
AmazonSoon
Catalog, cart, orders, inventory.
ShopifySoon
Multi-tenant storefronts.
Payment SystemSoon
Ledgers, idempotency, consistency.
Flash SaleSoon
Extreme spikes, oversell prevention.
SplitwiseSoon
Shared expenses and balances.
Architectures · Location & Logistics
Ride-Sharing (Uber)→
H3 hexagons match riders & drivers in real time.
Google MapsSoon
Tiles, routing, ETA.
Food DeliverySoon
Three-sided marketplace + dispatch.
AirbnbSoon
Search, availability, booking.
Architectures · Storage & Collaboration
Google DriveSoon
Chunked file storage and sync.
Google DocsSoon
Real-time collaborative editing (OT/CRDT).
GmailSoon
Mail storage, search, delivery.
PastebinSoon
Store and serve text snippets.
Architectures · Search, Ranking & Infra
URL Shortener (Bitly)→
Sync shorten, async analytics (NSQ), Z Proxy.
Web Search (Google)→
Crawl, inverted index, PageRank + signals.
AutocompleteSoon
Typeahead suggestions from a trie at scale.
Web CrawlerSoon
Polite, distributed crawling.
LeaderboardSoon
Real-time ranking at scale.
Notification SystemSoon
Reliable fan-out push/email/SMS.