12 · Engineering craft
Networking
HTTP, caching, WebSockets, and everything above the socket.
The pipe between your app and the data. Real-time, protocols, and caching decisions dominate system-design rounds.
HTTP & protocols
| Topic | Difficulty | Time | Tags | Best Resources |
|---|---|---|---|---|
| HTTP methods, status codes, headers | 🟢 | 45m | #http #basics |
MDN: HTTP ⭐ |
| HTTP/1.1 vs HTTP/2 | 🟡 | 45m | #http #performance |
web.dev: HTTP/2 ⭐ |
| HTTP/3 & QUIC | 🔴 | 45m | #http #performance |
Cloudflare: HTTP/3 ⭐ |
| TLS / handshake | 🟡 | 45m | #tls #security |
Cloudflare: TLS handshake ⭐ |
| DNS | 🟢 | 30m | #dns #basics |
Cloudflare: DNS ⭐ |
| Fetch, XHR & request cancellation | 🟢 | 45m | #fetch #api |
MDN: Fetch ⭐ |
API styles
| Topic | Difficulty | Time | Tags | Best Resources |
|---|---|---|---|---|
| REST API design | 🟡 | 1h | #rest #api |
MDN: REST ⭐ |
| GraphQL | 🟡 | 1.5h | #graphql #api |
graphql.org: learn ⭐ |
| gRPC / gRPC-Web | 🔴 | 45m | #grpc #api |
grpc.io ⭐ |
| Pagination (cursor vs offset) | 🟡 | 45m | #api #large-data |
Flagship ⭐ |
Real-time
| Topic | Difficulty | Time | Tags | Best Resources |
|---|---|---|---|---|
| WebSocket | 🔴 | 1h | #realtime #websocket |
MDN: WebSocket ⭐ |
| Server-Sent Events (SSE) | 🟡 | 45m | #realtime #sse |
MDN: SSE ⭐ |
| Polling vs long-polling vs push | 🟡 | 45m | #realtime #patterns |
Ably: long-polling ⭐ |
| WebRTC (P2P) | 🔴 | 1h | #realtime #webrtc |
WebRTC ⭐ |
| WebTransport | 🔴 | 45m | #realtime #modern |
web.dev: WebTransport ⭐ |
Caching, CDN & reliability
| Topic | Difficulty | Time | Tags | Best Resources |
|---|---|---|---|---|
| HTTP caching (Cache-Control, ETag) | 🟡 | 1h | #caching |
MDN: HTTP caching ⭐ |
| CDN & edge caching | 🟡 | 45m | #cdn #caching |
Cloudflare: CDN ⭐ |
| Compression (gzip/brotli) | 🟢 | 30m | #performance |
web.dev ⭐ |
| Load balancing (client view) | 🟡 | 45m | #scale |
Cloudflare ⭐ |
| Rate limiting & retries/backoff | 🟡 | 45m | #reliability |
AWS: backoff & jitter ⭐ |
| Idempotency & request dedupe | 🟡 | 45m | #reliability |
Stripe: idempotency ⭐ |
❓ Rapid-fire networking interview questions
Real networking questions asked at the SDE-2 / senior level. Answer out loud, then verify above.
- HTTP/1.1 vs HTTP/2 vs HTTP/3 — what improved?
- WebSocket vs SSE vs polling — when do you use each?
- How does HTTP caching work (
Cache-Control,ETag,304)? - What is CORS and what triggers a preflight request?
- REST vs GraphQL — trade-offs?
- What is a CDN and how does it speed things up?
- What happens during a TLS handshake?
- What are idempotent HTTP methods?
- How do you cancel an in-flight request (AbortController)?
- Cursor vs offset pagination — why does it matter?
- How do you implement retries with exponential backoff?
- What is DNS and how does resolution work?
- What is gzip/brotli compression?
- How does content negotiation work?
- What is request idempotency and why does checkout need it?
Related: 09-performance · 13-state-management · 17-interview-patterns
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