ExpressJS Deploying ExpressJS Applications Syllabus

Deploying ExpressJS Applications syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Deploying ExpressJS Applications in ExpressJS, not a summary of it.

1. 1

   Preparing for Deployment

   2 topics

   • Environment Variables
   • Configuring Production Settings
2. 2

   Deployment Platforms

   3 topics

   • Deploying to Heroku
   • Deploying to AWS
   • Deploying to DigitalOcean
3. 3

   CI/CD Pipelines

   2 topics

   • Setting Up GitHub Actions
   • Using Jenkins
4. 4

   Monitoring and Maintenance

   3 topics

   • Logging
   • Health Checks
   • Scaling Applications

Deploying ExpressJS Applications flashcards for ExpressJS

18 of 51 cards from the Deploying ExpressJS Applications deck — real questions with worked answers.

1. What is an environment variable in the context of an ExpressJS application?

   A key-value pair defined outside the application code (in the OS or process environment) that supplies configuration such as secrets, ports, and connection strings without hardcoding them into source files.

2. In Node.js/Express, which object exposes all environment variables to your code?

   The global `process.env` object, e.g. `process.env.PORT` or `process.env.DATABASE_URL`.

3. What is the conventional file used to store environment variables locally, and which package loads it?

   A `.env` file, loaded by the `dotenv` package via `require('dotenv').config()`, which populates `process.env`.

4. Why should a `.env` file be added to `.gitignore`?

   Because it typically contains secrets (API keys, DB passwords, tokens); committing it exposes credentials in version control.

5. How do you make an Express app read its listening port from the environment with a fallback?

   Use `const port = process.env.PORT || 3000;` so the platform-assigned port is used in production and 3000 in local dev.

6. What is the standard environment variable used to indicate the runtime mode of an Express app, and its common production value?

   `NODE_ENV`, set to `production` in production (other common values are `development` and `test`).

7. What performance and behavior changes occur in Express when `NODE_ENV` is set to `production`?

   Express caches view templates, caches CSS from extensions, generates less verbose error output, and many middleware/libraries enable optimizations, improving performance.

8. What is the security risk of leaking stack traces in production error responses, and how does Express address it?

   Stack traces reveal internal paths and logic to attackers; when `NODE_ENV=production`, Express's default error handler omits the stack trace from the response body.

9. In production Express configuration, why should you enable `app.set('trust proxy', ...)` behind a load balancer or reverse proxy?

   So Express correctly reads client info from `X-Forwarded-*` headers (real client IP, protocol), which is needed for secure cookies, rate limiting, and HTTPS detection.

10. Which two popular middleware packages are commonly added to harden and compress a production Express app?

    `helmet` (sets secure HTTP headers) and `compression` (gzip/deflate compresses responses).

11. What is a process manager, and name the most common one used to keep Express apps running in production.

    A tool that runs, monitors, auto-restarts, and load-balances Node processes; the most common is PM2 (with `pm2 start app.js` and cluster mode).

12. What is Heroku in one sentence?

    A cloud Platform-as-a-Service (PaaS) that runs apps in managed containers called dynos, abstracting away server provisioning.

13. What is a Procfile in a Heroku deployment and what does a typical Express entry look like?

    A text file at the project root declaring process types/commands; a typical web process line is `web: node index.js` (or `web: npm start`).

14. How does Heroku assign the port your Express app must listen on?

    Heroku sets the `PORT` environment variable at runtime, so the app must use `process.env.PORT`; binding to a hardcoded port causes the app to fail to bind.

15. What is the primary command used to deploy code to Heroku with Git?

    `git push heroku main` (or `git push heroku master`), which triggers a build and release of the app.

16. How do you set an environment variable (config var) on Heroku from the CLI?

    `heroku config:set KEY=value`; you can view them with `heroku config` and remove with `heroku config:unset KEY`.

17. How does Heroku know how to build a Node.js/Express app during deployment?

    It detects the `package.json` and applies the Node.js buildpack, running `npm install` and (if present) the `build`/`start` scripts.

18. What is AWS Elastic Beanstalk and why is it convenient for deploying Express apps?

    A PaaS-like AWS service that automatically handles provisioning, load balancing, auto-scaling, and deployment of your app; you upload code and it manages the underlying EC2 infrastructure.

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