Level 5 exam — Node.js

Exam — fresh questions

12 brand-new questions to validate Pro level & deployment: TypeScript, performance, Docker, deployment & CI/CD.
Answer everything, then click Check: your score and explanations will appear.

5.1 · Recall

1. What is TypeScript compared to JavaScript?

A language with no connection A superset adding static typing (all valid JS is valid TS) A Node replacement that runs with no compilation A tool that removes all types

TS = JS + types: you declare types on top of your JavaScript, checked at compile time.

5.1 · Application

2. Salim passes a quantity as text where a number is expected. When is the error caught?

Never, it will go unnoticed Only if a customer complains At compile time by tsc, before any execution Only after going to production

Static typing catches the inconsistency before execution — not at runtime or in production.

5.1 · Arbitration

3. Salim is starting out in JavaScript and wants to learn everything in strict TypeScript at once. Decision?

Solidify JavaScript first, then adopt TS gradually (light then advanced) Drop JavaScript to learn only types Force TypeScript even on a one-line throwaway script Type everything in strict mode from day one

You only type well what you understand: JS first, types on top, step by step.

5.2 · Recall

4. Why is clustering necessary in Node?

Because Node is single-threaded: one process uses only one core Because Node cannot handle requests Because RAM is always insufficient It is never necessary

Cluster or PM2: one instance per core to use the whole multi-core server.

5.2 · Application

5. Salim's API slows down: the same catalogue queries keep hitting the database. First lever?

Delete the database Rewrite all loops at random Add servers without measuring Cache the catalogue and index slow queries

Cache + query optimisation: often the most profitable lever, guided by measurement.

5.2 · Application

6. Salim wants to optimise without targeting the wrong thing. What approach?

Never touch the code, whatever happens Optimise by intuition, without measuring Measure (profile) to find the real bottleneck, optimise in a targeted way, re-measure Optimise everything everywhere at the same time

Golden rule: measure before optimising — never blind premature optimisation.

5.3 · Recall

7. What does a Docker container hold?

Only the code, with no environment The application WITH its whole environment (Node, dependencies, config) Only decorative images Nothing at all, it is an empty folder

The container ships its environment: it runs identically everywhere.

5.3 · Application

8. Salim's app works on his machine but not on his colleague's. What does he do?

Reinstall Node at random until it works Give up the project Copy node_modules by hand onto each machine Write a Dockerfile (dependencies installed in the image) + .dockerignore

Dockerfile + build + run: same image, same behaviour — no more “it works on my machine”.

5.3 · Application

9. Salim must bring up app + database for a newcomer with one command. Which tool?

An email with screenshots Advanced Kubernetes from day one A shared spreadsheet Docker Compose (docker compose up: app + database together)

Compose describes the whole stack: instant onboarding, reproducible identically.

5.4 · Application

10. Salim deploys his API: where do the secret key and database password go?

Hard-coded in the code, it's simpler In the Git repository, to share them In environment variables on the platform, never in code or Git In a public code comment

Secrets out of code, the Dockerfile and Git — provided by the environment.

5.4 · Arbitration

11. Salim is starting out and must put his API online fast. Which choice?

Administer a full VPS from day one Start with a simple PaaS platform (connected repository, managed HTTPS) Never deploy, keep localhost Copy the files by hand to a server with no HTTPS

PaaS to start (simplicity); VPS for control when ready to take on maintenance.

5.4 · Arbitration

12. Before exposing real customer data, what must Salim do?

Get the infrastructure and access validated by the IT department, check hosts' current offers Remove logs and monitoring to go faster Deploy fast without telling anyone Publish the secrets to ease access

Sensitive data: IT-department validation, offers checked when choosing, HTTPS and monitoring in place.

What's next?

Score ≥ 80%: move on to Level 6 “In practice” — real cases, troubleshooting and the Node toolbox (NO exam).
Score 50-79%: re-read the explanations above — each one re-explains the concept — then redo the 48h challenges of the sections you missed.
Score < 50%: revisit cards 5.3 (image vs container) and 5.4 (CI vs CD), your two vital moves, before continuing.