Environment Variables

Environment variables are key-value pairs that configure your application at runtime. They're used for database connections, API keys, feature flags, and other settings that change between environments.

How environment variables work in Hydron

Environment variables in Hydron are:

Encrypted at rest — Sensitive values are encrypted with AES-256
Injected at runtime — Passed to Docker containers when they start
Per-service — Each service has its own set of variables
Never logged — Sensitive values are redacted from deployment logs

Setting environment variables

During code analysis

When Hydron analyzes your repository, it detects environment variables referenced in your code. Common patterns it recognizes:

process.env.DATABASE_URL (Node.js)
os.environ.get('SECRET_KEY') (Python)
ENV['REDIS_URL'] (Ruby)
.env file references

Detected variables appear in the service configuration with empty values for you to fill in.

Through the chat

Tell the AI to set environment variables:

"Set the DATABASE_URL for api-server to postgres://user:pass@host:5432/mydb"
"Add a STRIPE_SECRET_KEY variable to the payment service"
"Set NODE_ENV to production for all services"

Through the sidebar

Open the Services tab in the right sidebar
Click on a service
Find the Environment Variables section
Add, edit, or remove variables

The Services panel where you can configure environment variables per service

Common environment variables

Here are commonly used environment variables by category:

Application

Variable	Description	Example
`NODE_ENV`	Runtime environment	`production`
`PORT`	Server listen port	`3000`
`HOST`	Server bind address	`0.0.0.0`
`LOG_LEVEL`	Logging verbosity	`info`

Database

Variable	Description	Example
`DATABASE_URL`	Full connection string	`postgres://user:pass@host:5432/db`
`DB_HOST`	Database hostname	`postgres.internal`
`DB_PORT`	Database port	`5432`
`DB_NAME`	Database name	`myapp`
`DB_USER`	Database username	`app_user`
`DB_PASSWORD`	Database password	`(secret)`

Cache & Queue

Variable	Description	Example
`REDIS_URL`	Redis connection string	`redis://redis:6379`
`CACHE_TTL`	Cache time-to-live	`3600`

Authentication

Variable	Description	Example
`JWT_SECRET`	Token signing secret	`(secret)`
`SESSION_SECRET`	Session encryption key	`(secret)`
`OAUTH_CLIENT_ID`	OAuth client identifier	`abc123`
`OAUTH_CLIENT_SECRET`	OAuth client secret	`(secret)`

External services

Variable	Description	Example
`STRIPE_SECRET_KEY`	Payment processing	`sk_live_...`
`SMTP_HOST`	Email server	`smtp.gmail.com`
`S3_BUCKET`	Storage bucket name	`my-app-uploads`
`API_KEY`	Third-party API key	`(secret)`

Cross-service references

When services within the same project need to communicate, Hydron can automatically configure cross-service environment variables.

For example, if your api-server depends on a postgres service, Hydron sets:

api-server:
  DATABASE_URL = postgres://user:pass@postgres:5432/mydb
                                      ^^^^^^^^
                                      Internal service name

Services within the same deployment can reach each other by their service name as the hostname.

Best practices

Never hardcode secrets — Always use environment variables for API keys, passwords, and tokens
Use descriptive names — DATABASE_URL is better than DB
Group related variables — Use prefixes like SMTP_, AWS_, STRIPE_ for organization
Keep defaults sensible — Set non-sensitive defaults where appropriate (ports, log levels)
Document required variables — Add descriptions to help team members understand what each variable does

Updating variables after deployment

To update environment variables after your app is deployed:

Change the values through the chat or sidebar
Ask the AI to redeploy the affected service
The container restarts with the new values

Changes to environment variables require a container restart to take effect.