// YOUTUBE COMPANION DIAGRAMS
The diagrams behind the videos.
The 27 diagram boards and decks from Akhil's YouTube system-design videos — Discord, WhatsApp, TikTok, Stripe, YouTube and more. Follow along, or revisit any breakdown.
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27 diagrams
How Airtable Models a Flexible Database
The data model that lets a spreadsheet behave like a relational database — without the user ever seeing a schema.
How Google Colab Runs Untrusted Code Safely
Isolating millions of strangers' notebooks with sandboxing, gVisor, and disposable VMs.
How Datadog Ingests Trillions of Events
The pipeline that swallows metrics, traces, and logs from millions of hosts in real time.
How DeepSeek Trained a Frontier Model for Less
The architecture and training tricks behind a GPT-class model at a fraction of the GPU cost.
How Discord Stores Trillions of Messages
The migration from Cassandra to ScyllaDB, and how message history stays fast at that scale.
How Dropbox Scaled Storage On and Off AWS
Block storage, Magic Pocket, and the economics of leaving the cloud you grew up on.
Gmail — A System Design Walkthrough
From SMTP ingestion to search: the moving parts behind the world's default inbox.
How Gmail Handles 44 Trillion Emails
Storage, indexing, and spam at a scale where every byte of overhead is measured in petabytes.
How Google Maps Routes the Planet
Tiling the world, contraction hierarchies, and live traffic — the graph problem at global scale.
How Google Search Indexes the Web
Crawling, the inverted index, and serving a query in under 200ms across billions of pages.
How Instagram Scales PostgreSQL
Sharding, logical IDs, and the disciplined Postgres patterns that carried Instagram to a billion users.
How Jira Models Projects at Scale
Custom fields, workflows, and permissions — modeling infinite flexibility without melting the database.
How Notion Designed Its Block Data Model
Everything is a block: the recursive data model that makes docs, databases, and pages one primitive.
How Reddit Serves the Front Page
Vote counting, caching, and the read-heavy architecture behind the internet's front page.
How Replit's AI Agent Ships Code
Orchestrating an autonomous coding agent — sandboxes, tools, and the loop that writes and runs code.
How Roblox Handles 47M Concurrent Players
Game servers, matchmaking, and the edge network that keeps a virtual world in sync.
How Slack Delivers Real-Time Messaging
The channel server, WebSocket fan-out, and how Slack keeps millions of tabs live at once.
How Stripe Runs Ruby at Scale
Idempotency, sorbet types, and the reliability engineering behind moving money in Ruby.
How TikTok's Recommendation Engine Works
The candidate → ranking → serving pipeline that makes the For You feed frighteningly good.
How WhatsApp Serves 2 Billion Users
Erlang, a tiny team, and the messaging architecture that famously ran on a shoestring.
How YouTube Streams 1 Billion Hours a Day
Transcoding, the CDN, and adaptive bitrate — delivering more video than the rest of the web combined.
Why AWS Builds Its Own Everything
Nitro, Graviton, custom silicon — the vertical-integration playbook behind the world's biggest cloud.
How CrowdStrike Crashed 8.5 Million Computers
A single content update, a kernel driver, and the anatomy of the largest IT outage in history.
Why Amazon Killed Its Own Microservices
The monitoring service Prime Video rebuilt as a monolith — and the 90% cost cut that made headlines.
Snowflake — The Architecture
Separating storage from compute: the design that let a data warehouse scale each independently.
Starlink — How It Routes Packets
Phased-array antennas, laser inter-satellite links, and routing IP through low-earth orbit.
BitTorrent — A Protocol Teardown
Pieces, peers, and the tit-for-tat algorithm behind the internet's most durable P2P protocol.