Environment Variables: Patterns and Gotchas

Why Configuration Matters

Hardcoded values are one of the fastest ways to break production systems. Environment variables allow the same codebase to run in development, staging, and production without modification.

Accessing Environment Variables

const port = Number(process.env.PORT ?? 3000);
console.log('Running on port:', port);

process.env Is Always String

All values in process.env are strings. You must manually convert them to numbers or booleans.

Validation Strategy

Never assume environment variables exist. Validate them at startup.

function requireEnv(name: string): string {
  const value = process.env[name];
  if (!value) {
    throw new Error(`Missing environment variable: ${name}`);
  }
  return value;
}

Configuration Layer Pattern

Create a dedicated config module that reads and validates environment variables once, then exports typed configuration values.

Secrets

Never commit secrets to version control. Use environment variables or secret managers in production systems.

Production Perspective

• Validate at startup.
• Fail fast if config is invalid.
• Separate config from business logic.