Environment Variables

Environment variables are a set of dynamic named values that can affect the way running processes will behave on a computer. In web development, they are a crucial tool for managing application configuration that varies between deployment environments (e.g., development, testing, production). A key principle of building scalable applications is to maintain a strict separation between code and configuration. Your codebase should be the same across all environments, but the configuration—such as the database connection URL, API keys for third-party services, or the port number to run the server on—will be different. Storing this configuration directly in your code is a bad practice. It's insecure, as it can expose sensitive credentials if your code is made public, and it's inflexible, as you would need to change the code to deploy to a new environment. Environment variables solve this problem. You can access them in your code (in Node.js, via the `process.env` object), but their values are set in the environment where the code is running. For local development, it's common to use a `.env` file (which should be added to your `.gitignore`) to store these variables. In production, deployment platforms like Heroku, Vercel, and AWS provide a secure way to set environment variables for your deployed application. This ensures that your sensitive keys and configuration are kept separate from your version-controlled codebase.