HeyJaredSystem Design Twitter Course
Over 5 weeks, you'll build a complete Twitter-like platform that scales from 1,000 to 10 million users. You'll experience every architectural decision point, every performance bottleneck, every moment when adding more servers makes things worse instead of
- Indexed issues, last 90 days
- 12
- Latest publication
- Sep 30, 2026
- Audience
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- Earliest in this view
- Aug 17, 2026
Latest issues
Lesson 47: Key Hygiene — Rotation, Recovery, and Device Management (opens the original)
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What We’re Building TodayA BIP-39 key deriver that turns 12 words into a deterministic Ed25519 keypair and a did:key identifier — no key material ever touches disk in plaintext.A rotation ceremony where an old key signs a new key’s DID, letting NEXUS swap an account’s active credential without resetting its follow graph or reputation score.A 3-of-5 Shamir secret-sharing recovery scheme: split a seed into five shares, hand them to five contacts, and reconstruct from any three — with a cryptograph
Lesson 46: Keys Instead of Passwords — Implementing DIDs (opens the original)
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What We’re Building TodayA did:key identity layer that replaces password/JWT login with a cryptographic challenge-response handshake — no shared secret ever crosses the wire.A measured full-handshake latency of P50 = 0.23ms, P99 = 0.80ms in-process, verified over 50 iterations against the registry’s target.A migration path that converts 50 legacy JWT sessions into DID identities without invalidating a single user’s account.Why This MattersIn 2023, Okta’s support system was breached through a sto
Lesson 45 — Phase 2 Milestone: The Autonomous Community Manager (opens the original)
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What We’re Building TodayA single orchestration harness that wires classification, moderation, summarization, semantic feed ranking, and the ReAct engagement agent into one running systemA 30-minute virtual-clock simulation ingesting 500 synthetic tweets per minute (15,000 total), with every component operating on the same shared engine stateProof, via a passing verification suite and a recorded metric dashboard, that five previously isolated Phase 2 components compose correctly under sustained
Lesson 44 — The Explanation UI: Making AI Decisions Transparent (opens the original)
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What We’re Building TodayAn explainDecision() service that turns Day 34’s chain-of-thought reasoning into a plain-language “Why did this appear?” panel, rendered live in the NEXUS feed UIA correction workflow — “This was wrong” — that flips a post’s accuracy flag in place and appends the reasoning trace to a fine-tuning dataset the Day 42 feedback loop can consumeAn accuracy dashboard computing per-category accuracy and a 30-day trend, both served in under 20ms P99 on 200 posts and 600 correctio
Lesson 43: The Multilingual Pipeline — Language-Agnostic Classification (opens the original)
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What We’re Building TodayA keyword-signal embedder that projects text from five languages (English, Spanish, French, German, Hindi) into one shared 5-dimensional topic-vector space, with zero per-language modelsA cross-language similarity verifier that proves an English tweet about elections and a Spanish tweet about elections land closer together than two English tweets about different topicsA global trending aggregator that deduplicates the same story across languages instead of counting it on
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