System Design Fundamentals · Week 4–5

Eviction policies: LRU, LFU, TTL

01 / 13Present00:00

System Design Fundamentals • Week 4–5

01 / 13

Eviction policies: LRU, LFU, TTL

The fastest query is the one you never run.

StackShade deck

Predict → explain → retrieve

COURSE CONTENTS

Eviction policies: LRU, LFU, TTL

01Foundations of ScalabilityWeek 1 · 5 topics0/5

Vertical vs horizontal scaling10 min Latency, throughput, bandwidth — with real numbers12 min Interactive: numbers every engineer should know10 min Availability, nines, and single points of failure12 min Back-of-envelope estimation: QPS & storage15 min

02Networking Essentials for DesignWeek 1–2 · 4 topics0/4

OSI model refresher (interactive)15 min DNS, TCP vs UDP, TLS — the design interview essentials14 min HTTP deep dive: methods, status codes, keep-alive12 min Proxies, reverse proxies and why every design has one12 min

03APIs & Communication StylesWeek 2 · 5 topics0/5

REST design: resources, verbs, idempotency14 min GraphQL & gRPC: when each beats REST12 min Long polling vs Server-Sent Events vs WebSockets12 min Interactive: pick the right protocol for 6 scenarios10 min Design the API contract for a tiny URL shortener30 min

04Databases: SQL, NoSQL & IndexesWeek 3 · 5 topics0/5

Relational model, ACID transactions14 min NoSQL flavors: key-value, document, columnar, graph14 min Interactive: how a B-tree index finds rows12 min N+1 queries, connection pooling, slow query basics12 min Pick the database for 5 app scenarios (justify each)20 min

05Scaling Databases: Replication & ShardingWeek 3–4 · 5 topics0/5

Leader-follower & multi-leader replication14 min Read replicas and the read-your-writes problem12 min Sharding: keys, hotspots, and resharding pain14 min Interactive: shard a users table 3 ways, compare12 min CAP theorem and what it means in practice12 min

06Caching EverywhereWeek 4–5 · 5 topics0/5

Cache-aside vs write-through vs write-behind12 min Eviction policies: LRU, LFU, TTL10 min CDNs and edge caching12 min Interactive: cache stampede & how to stop it10 min Design caching for a news feed (what, where, TTL?)25 min

07Load Balancing & Async SystemsWeek 5 · 5 topics0/5

L4 vs L7 load balancers and routing algorithms12 min Load balancer playground: round-robin vs least-connections10 min Message queues, pub/sub, delivery guarantees14 min Backpressure and graceful degradation12 min Design: notification service that survives 100x spikes35 min

08Your First System DesignsWeek 6 · 5 topics0/5

The 6-step design interview framework14 min Design a URL shortener (full walkthrough)20 min Design Pastebin (and how it differs)16 min Solo design: rate limiter + leaderboard45 min Self-review with the rubric: what did you miss?15 min