Question 1

How does DNS resolution work?

Accepted Answer

**Target Audience:** Beginners to system design — you have used a browser; no networking background assumed.
**Difficulty:** Easy
**Verified with:** Node 22.22 and Python 3.12 (both print identical output).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Behaviour claims come from running the example; the **Verified** section quotes the full output.

## 1. Why This Even M

Question 2

What is the difference between a reverse proxy and a forward proxy?

Accepted Answer

**Target Audience:** Beginners to system design — you know a browser talks to a server; no networking background assumed.
**Difficulty:** Easy
**Verified with:** Node 22.22 and Python 3.12 (both print identical output).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Behaviour shown comes from running the example; the **Verified** section quotes the full output.

## 1. Wh

Question 3

Edge caching on Cloudflare — how do you get 95%+ hit rate without stale data?

Accepted Answer

**Target Audience:** Intermediate — you know what a CDN does; Cloudflare-specific settings and terms are explained here.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (both print identical output). Cloudflare product behaviour is taken from Cloudflare documentation and changelog entries cited inline, checked in October 2026.

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words

Question 4

What is the difference between REST and GraphQL?

Accepted Answer

**Target Audience:** Beginners to system design — you have called an HTTP API; no GraphQL experience assumed.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (both print identical output).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Request counts and byte sizes come from running the example; the **Verified** section quotes the full output.

## 1.

Question 5

When do you use a read replica vs a cache?

Accepted Answer

**Target Audience:** Beginners to system design — you know what a database and a query are; replication and caching are explained here.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (both print identical output).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Behaviour claims (stale reads, counts) come from running the example; the **Verified** sec

Question 6

What is database sharding?

Accepted Answer

**Target Audience:** Beginners to system design who know what a database table is; no distributed-systems background assumed.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (both print identical output). Notion figures are cited from the Notion engineering blog; DynamoDB limits from the AWS DynamoDB developer guide.

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the words an interviewer e

Question 7

What is a CDN and how does it work?

Accepted Answer

**Target Audience:** Beginners to system design — you know what a web server is; no networking background assumed.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (both print identical output).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Hit ratios and fetch counts come from running the example; the **Verified** section quotes the full output.

##

Question 8

How would you design an edge-native app on Cloudflare Workers + R2?

Accepted Answer

**Target Audience:** Beginners to edge and serverless design — you know HTTP, caching and a database; every Cloudflare product used is explained when it first appears.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (both print identical output). Cloudflare limits and prices are from the Cloudflare developer docs (Workers limits, Workers pricing, R2 pricing, storage overview, Cache API, Durable Objects concepts, D1 overview), checked October 2026; they change, so recheck bef

Question 9

How does caching work end-to-end (where, what, when) — cache-aside vs write-through?

Accepted Answer

# How Does Caching Work End-to-End? Where, What, and When (Cache-Aside vs. Write-Through) **Target Audience:** Junior & Senior Software Engineers preparing for System Design Interviews — assumes basic familiarity with the idea of a cache. **Difficulty:** Medium > This doc builds on the Caching guide (eviction policies, LRU) and the

Question 10

How does caching improve system performance?

Accepted Answer

**Target Audience:** Beginners to system design — you know what a database query is; no caching background assumed.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (both print identical output).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Hit ratios, latencies and counts come from running the example; the **Verified** section quotes the full outpu

SYSTEM DESIGNDECODED.

Easy

How does DNS resolution work?

What is the difference between a reverse proxy and a forward proxy?

Medium

Edge caching on Cloudflare — how do you get 95%+ hit rate without stale data?

What is the difference between REST and GraphQL?

When do you use a read replica vs a cache?

What is database sharding?

What is a CDN and how does it work?

How would you design an edge-native app on Cloudflare Workers + R2?

How does caching work end-to-end (where, what, when) — cache-aside vs write-through?

How does caching improve system performance?

Hard

How would you design a URL shortener like TinyURL? (Pastebin / Bit.ly)

What is KV-cache and how does prefix caching speed up LLM inference?

How would you design a typeahead/autocomplete system?

How would you design a URL shortener like TinyURL?

How would you design a metrics monitoring and alerting system?

How would you design Google Drive?