Drill library163 drills · filtered to System design, Staff bar
Prescribed for you · written from your scorecard on 24 May
Last round: Approaching on Framing — we held back the architecture-first reflex.
Restate the read/write ratio inside ninety seconds
Framing drill12mVoice-only
Targets: Framing · Pacing
Design rate limiting for Stripe's public API
System designStaff30m
Targets: Framing · Evidence
Quantify the load before the architecture
Framing drill15mHard mode
Targets: Framing
Added this week · 6 drills
Design a notification fan-out system at Twitter scale
Read/write asymmetry, celebrity tier, push vs pull, idempotent delivery; one billion users.
Design idempotent payment retries for Stripe's charges API
Idempotency keys, retry storms, exactly-once semantics, partial-failure recovery.
Design a search-as-you-type system for Linear's command bar
Sub-150ms p95 over 80k workspaces, prefix matching, ranking signals, client-side cache.
Design rate limiting for a public REST API at 100k req/s
Token bucket vs leaky bucket, per-key vs per-IP, distributed counters, fairness under burst.
Design a multi-region cache invalidation protocol for Cloudflare
Consistency model, purge fan-out under 5s globally, the cost of stale reads, conflict resolution.
Design a feature-flag service for a thousand engineers
Targeting rules, low-latency SDK reads, gradual rollouts, audit trail, kill-switch path.
Core library · 157 more drills
Design the URL shortener behind a marketing team
Key generation, collision avoidance, analytics fan-out, redirect latency at the edge.
Design a chat backend that supports a thousand concurrent rooms
Connection model, presence, message ordering, history sync, mobile reconnect semantics.
Design a queue with at-least-once delivery and visibility timeouts
SQS-shaped semantics, in-flight bookkeeping, dead letters, poison pill handling.
Design an analytics ingest pipeline for ten billion events a day
Backpressure, batching, schema evolution, late-arriving data, replay correctness.
Design a typeahead service for a hundred million product SKUs
Inverted index, trie compression, personalisation, the cost of relevance at the edge.
Design a metering service that bills on usage at API granularity
Counter precision, late events, double counting, the cost of correctness vs. cost of speed.
The library is the medicine cabinet, not the gym membership wall.
Pick one drill, run it. A scorecard arrives twenty minutes later.