Environment separation - dev, staging, and production

Environment separation is the discipline that keeps development and production from colliding. This lesson covers how to design and enforce it.

Why separation matters

Without separation:

• A developer’s experiment takes down production.
• A production change breaks development.
• Data leaks between users.
• A test script in dev sends spam from prod.

Separation prevents these by isolating the environments.

The standard environments

• Development: where developers work. May have real data (anonymised) or synthetic data.
• Staging: mirrors production. Used for final testing before deploy.
• Production: real users. The most protected.

Some teams add:

• QA: dedicated testing environment.
• Pre-prod: production-like, with synthetic traffic.
• DR: the disaster recovery site.

How to enforce

Networking

Separate VPCs, subnets, or physical networks:

prod-vpc:    10.0.0.0/16
staging-vpc: 10.1.0.0/16
dev-vpc:     10.2.0.0/16

No direct routing between dev and prod. Access via bastion or VPN.

IAM

Different credentials per environment:

alice@prod-db    (PostgreSQL on production)
alice@staging-db (PostgreSQL on staging)
alice@dev-db     (PostgreSQL on dev)

Different passwords, keys, or roles. Production credentials are the most protected.

Configuration

Different config files, secrets, database names:

# Production
DATABASE_URL=postgres://prod-db:5432/app
SECRET_KEY=long_random_string

# Staging
DATABASE_URL=postgres://staging-db:5432/app
SECRET_KEY=different_random_string

# Dev
DATABASE_URL=postgres://localhost:5432/app_dev
SECRET_KEY=dev_only_key

Tools like Vault, sops, or 12-factor config handle this.

Code

The same code runs in all environments. Different config, not different code.

git branch:
  main        - production deploy
  staging     - staging deploy
  develop     - dev deploy

PRs target develop, get merged to staging for testing, then to main for production.

Common pitfalls

• Shared database: dev and prod share a database. One wipes, both lose.
• Shared credentials: prod password in dev config.
• Direct access to prod from dev: no firewall separation.
• Cross-environment data flow: dev script reads prod data.

A clear separation is the foundation of safe deploys.

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