database

What this skill does

# Database

Add official Railway database services. These are maintained templates with pre-configured volumes, networking, and connection variables.

For non-database templates, see the `templates` skill.

## When to Use

- User asks to "add a database", "add Postgres", "add Redis", etc.
- User needs a database for their application
- User asks about connecting to a database
- User says "add postgres and connect to my server"
- User says "wire up the database"

## Decision Flow

**ALWAYS check for existing databases FIRST before creating.**

```
User mentions database
        │
  Check existing DBs first
  (query env config for source.image)
        │
   ┌────┴────┐
 Exists    Doesn't exist
    │           │
    │      Create database
    │      (CLI or API)
    │           │
    │      Wait for deployment
    │           │
    └─────┬─────┘
          │
    User wants to
    connect service?
          │
    ┌─────┴─────┐
   Yes         No
    │           │
Wire vars    Done +
via env     suggest wiring
skill
```

## Check for Existing Databases

Before creating a database, check if one already exists.

For full environment config structure, see [environment-config.md](references/environment-config.md).

```bash
railway status --json
```

Then query environment config and check `source.image` for each service:

```graphql
query environmentConfig($environmentId: String!) {
  environment(id: $environmentId) {
    config(decryptVariables: false)
  }
}
```

The `config.services` object contains each service's configuration. Check `source.image` for:

- `ghcr.io/railway/postgres*` or `postgres:*` → Postgres
- `ghcr.io/railway/redis*` or `redis:*` → Redis
- `ghcr.io/railway/mysql*` or `mysql:*` → MySQL
- `ghcr.io/railway/mongo*` or `mongo:*` → MongoDB

## Available Databases

| Database | Template Code |
|----------|---------------|
| PostgreSQL | `postgres` |
| Redis | `redis` |
| MySQL | `mysql` |
| MongoDB | `mongodb` |

## Prerequisites

Get project context:
```bash
railway status --json
```

Extract:
- `id` - project ID
- `environments.edges[0].node.id` - environment ID

Get workspace ID (not in status output):
```bash
bash <<'SCRIPT'
scripts/railway-api.sh \
  'query getWorkspace($projectId: String!) {
    project(id: $projectId) { workspaceId }
  }' \
  '{"projectId": "PROJECT_ID"}'
SCRIPT
```

## Adding a Database

### Step 1: Fetch Template

```bash
bash <<'SCRIPT'
scripts/railway-api.sh \
  'query template($code: String!) {
    template(code: $code) {
      id
      name
      serializedConfig
    }
  }' \
  '{"code": "postgres"}'
SCRIPT
```

This returns the template's `id` and `serializedConfig` needed for deployment.

### Step 2: Deploy Template

```bash
bash <<'SCRIPT'
scripts/railway-api.sh \
  'mutation deployTemplate($input: TemplateDeployV2Input!) {
    templateDeployV2(input: $input) {
      projectId
      workflowId
    }
  }' \
  '{
    "input": {
      "templateId": "TEMPLATE_ID",
      "serializedConfig": SERIALIZED_CONFIG,
      "projectId": "PROJECT_ID",
      "environmentId": "ENVIRONMENT_ID",
      "workspaceId": "WORKSPACE_ID"
    }
  }'
SCRIPT
```

**Important:** `serializedConfig` is the exact object from the template query, not a string.

## Connecting to the Database

After deployment, other services connect using reference variables.

For complete variable reference syntax and wiring patterns, see [variables.md](references/variables.md).

### Backend Services (Server-side)

Use the private/internal URL for server-to-server communication:

| Database | Variable Reference |
|----------|-------------------|
| PostgreSQL | `${{Postgres.DATABASE_URL}}` |
| Redis | `${{Redis.REDIS_URL}}` |
| MySQL | `${{MySQL.MYSQL_URL}}` |
| MongoDB | `${{MongoDB.MONGO_URL}}` |

### Frontend Applications

**Important:** Frontends run in the user's browser and cannot access Railway's private network. They must use public URLs or go through a backend API.

For direct database access from frontend (not recommended):
- Use the public URL variables (e.g., `${{MongoDB.MONGO_PUBLIC_URL}}`)
- Requires TCP proxy to be enabled

Better pattern: Frontend → Backend API → Database

## Example: Add PostgreSQL

```bash
bash <<'SCRIPT'
# 1. Get context
railway status --json
# Extract project.id and environment.id

# 2. Get workspace ID
scripts/railway-api.sh \
  'query { project(id: "proj-id") { workspaceId } }' '{}'

# 3. Fetch Postgres template
scripts/railway-api.sh \
  'query { template(code: "postgres") { id serializedConfig } }' '{}'

# 4. Deploy template
scripts/railway-api.sh \
  'mutation deploy($input: TemplateDeployV2Input!) {
    templateDeployV2(input: $input) { projectId workflowId }
  }' \
  '{"input": {"templateId": "...", "serializedConfig": {...}, "projectId": "...", "environmentId": "...", "workspaceId": "..."}}'
SCRIPT
```

### Then Connect From Another Service

Use `environment` skill to add the variable reference:

```json
{
  "services": {
    "<backend-service-id>": {
      "variables": {
        "DATABASE_URL": { "value": "${{Postgres.DATABASE_URL}}" }
      }
    }
  }
}
```

## Response

Successful deployment returns:
```json
{
  "data": {
    "templateDeployV2": {
      "projectId": "e63baedb-e308-49e9-8c06-c25336f861c7",
      "workflowId": "deployTemplate/project/e63baedb-e308-49e9-8c06-c25336f861c7/xxx"
    }
  }
}
```

## What Gets Created

Each database template creates:
- A service with the database image
- A volume for data persistence
- Environment variables for connection strings
- TCP proxy for external access (where applicable)

## Error Handling

| Error | Cause | Solution |
|-------|-------|----------|
| Template not found | Invalid template code | Use: `postgres`, `redis`, `mysql`, `mongodb` |
| Permission denied | User lacks access | Need DEVELOPER role or higher |
| Project not found | Invalid project ID | Run `railway status --json` for correct ID |

## Example Workflows

### "add postgres and connect to the server"

1. Check existing DBs via env config query
2. If postgres exists: Skip to step 5
3. If not exists: Deploy postgres template (fetch template → deploy)
4. Wait for deployment to complete
5. Identify target service (ask if multiple, or use linked service)
6. Use `environment` skill to stage: `DATABASE_URL: { "value": "${{Postgres.DATABASE_URL}}" }`
7. Apply changes

### "add postgres"

1. Check existing DBs via env config query
2. If exists: "Postgres already exists in this project"
3. If not exists: Deploy postgres template
4. Inform user: "Postgres created. Connect a service with: `DATABASE_URL=${{Postgres.DATABASE_URL}}`"

### "connect the server to redis"

1. Check existing DBs via env config query
2. If redis exists: Wire up REDIS_URL via environment skill → apply
3. If no redis: Ask "No Redis found. Create one?"
   - Deploy redis template
   - Wire REDIS_URL → apply

## Composability

- **Connect services**: Use `environment` skill to add variable references
- **View database service**: Use `service` skill
- **Check logs**: Use `deployment` skill