How would you Design?

Interview-style prompts: clarify requirements, estimate scale, draw components, and defend tradeoffs. Each guide walks the full loop—functional and non-functional requirements, napkin math, APIs, storage, and failure modes. For the structured curriculum—fundamentals, patterns, estimation, and L4–Staff interview frameworks—see SysDesign Core. For product deep dives (how Reddit or Uber actually work), see Case Studies.

SysDesign Core — interview & theory

Use this track alongside the prompts below: RADIO framework, 45-minute clock, database selection, caching, and staff-level trade-off analysis.

Capstone
SysDesign Core

Dual learning and interview tracks—fundamentals, distributed systems, case studies, patterns library, and copy-ready cheat sheets.

Classic system design prompts

Foundational scenarios asked at product companies—start here if you are preparing for backend or platform interviews.

Guide
Design Instagram

You’ll solve hybrid fan-out for feeds and celebrities, media upload and CDN, Stories TTL, timelines in Cassandra—and map failure points and failure modes.
Guide
Design event booking

You’ll model seat holds and atomic inventory, virtual waiting rooms for on-sales, payment confirm sagas, and map failure points and failure modes (oversell, orphan holds).
Guide
Design a distributed cache

You’ll shard with consistent hashing, replicate primaries, handle hot keys and TTL stampedes, migrate slots safely—and map failure points and failure modes.
Guide
Design a distributed rate limiter

You’ll compare token bucket vs sliding window, enforce limits with Redis and Lua, handle multi-region fairness, and map failure points and failure modes.
Guide
Design a URL shortener

You’ll size read-heavy traffic, pick Base62 vs hash keys, cache redirects in Redis, and explain 301 vs 302 for analytics.
Guide
Design a payment system

You’ll model auth/capture/refund, double-entry ledger, idempotency, webhooks, reconciliation—and map failure points and failure modes end to end.
Guide
Design a notification system

You’ll fan out push, email, SMS, and in-app delivery with priority queues, templates, preferences, retries, and a full failure-point and failure-mode map.
Guide
Design Netflix-style streaming

You’ll size CDN egress and segment traffic, design transcode ladders and HLS playback, sign URLs, handle regional catalog—and map failure points and failure modes.

AI system design

RAG, regulated LLMs, real-time retrieval, and production AI—grouped in a dedicated track.

6 guides
Design AI Systems

Financial RAG, production pipelines, sub-200ms retrieval, regulated banking LLMs, live trading knowledge, and air-gapped assistants.