Nền tảng tới senior trong 3 tuần
21 ngày đi hết roadmap theo tier — mọi track, mọi câu trọng điểm, đọc cả phần khái niệm và cơ chế.
0/339 câu đạt ≥ 3
Dành cho khi có 2–4 tuần và muốn chắc từ nền tảng. Đi đúng thứ tự tier của roadmap, mỗi ngày 1–2 track.
- Đọc TL;DR → Khái niệm cốt lõi → Cheat sheet, rồi luyện essentials.
- Sau essentials, nếu còn sức: vào trang track, lọc Chưa chấm và làm thêm 5–10 câu Hard/Senior.
- Mỗi cuối tuần (ngày 7, 14, 21) là ngày tổng ôn: mở Random với pool Chưa vững (≤2).
- EasyWalk me through what happens, at the network level, when a browser loads
https://shop.example.comfor the first time. - MediumExplain head-of-line blocking in HTTP/1.1, HTTP/2 and HTTP/3. Which layer does each version fix it at?
- MediumDoes CORS protect your API from CSRF? Explain with a concrete request that still goes through.
- EasyWhat do the HTTP status codes 502, 503 and 504 mean when you see them from a reverse proxy?
- HardYou are migrating an API to a new cluster by changing its DNS record. One hour after the switch, 20% of traffic still hits the old cluster. Explain why and plan it better next time.
- MediumLayer 4 vs Layer 7 load balancing — what can each see and do, and where does TLS terminate in each?
- HardAfter scaling your Socket.IO/WebSocket server from 1 to 4 instances, users randomly miss messages and some clients reconnect in a loop. What's wrong?
- Senior probingHow do you set a consistent timeout and retry policy across a chain of client → CDN → LB → API → downstream service → DB?
- EasyConcurrency vs parallelism — explain with Node.js as the example.
- Medium
clustervsworker_threadsvs running multiple containers — how do you use more CPU cores for a Node API? - HardA checkout endpoint sometimes oversells the last item. Explain the race and give two correct fixes at the database level.
- HardYour Node API's p99 latency jumps from 50 ms to 2 s whenever a nightly report runs in the same process, though CPU shows only one core busy. Investigate and fix.
- MediumWhat does "backpressure" mean, and how do Node streams implement it?
- MediumPessimistic locking vs optimistic concurrency control — how do you choose for updating an order or inventory row?
- HardWhy is
crypto.pbkdf2Syncorbcrypt.hashSyncin a login handler a production incident waiting to happen, even at low traffic? - Senior probingHow do you decide between database locks, a Redis lock, and designing for idempotency when two actors can modify the same resource?
- EasyWalk me through what happens, at the network level, when a browser loads