# Durable Objects Configuration

## Basic Setup

```jsonc
{
  "name": "my-worker",
  "main": "src/index.ts",
  "compatibility_date": "2025-01-01",  // Use latest; ≥2024-04-03 for RPC
  "durable_objects": {
    "bindings": [
      { 
        "name": "MY_DO",                // Env binding name
        "class_name": "MyDO"            // Class exported from this worker
      },
      { 
        "name": "EXTERNAL",             // Access DO from another worker
        "class_name": "ExternalDO", 
        "script_name": "other-worker"
      }
    ]
  },
  "migrations": [
    { "tag": "v1", "new_sqlite_classes": ["MyDO"] }  // Prefer SQLite
  ]
}
```

## Binding Options

```jsonc
{
  "name": "BINDING_NAME",
  "class_name": "ClassName",
  "script_name": "other-worker",        // Optional: external DO
  "environment": "production"           // Optional: isolate by env
}
```

## Jurisdiction (Data Locality)

Specify jurisdiction at ID creation for data residency compliance:

```typescript
// EU data residency
const id = env.MY_DO.idFromName("user:123", { jurisdiction: "eu" })

// Available jurisdictions
const jurisdictions = ["eu", "fedramp"]  // More may be added

// All operations on this DO stay within jurisdiction
const stub = env.MY_DO.get(id)
await stub.someMethod()  // Data stays in EU
```

**Key points:**
- Set at ID creation time, immutable afterward
- DO instance physically located within jurisdiction
- Storage and compute guaranteed within boundary
- Use for GDPR, FedRAMP, other compliance requirements
- No cross-jurisdiction access (requests fail if DO in different jurisdiction)

## Migrations

```jsonc
{
  "migrations": [
    { "tag": "v1", "new_sqlite_classes": ["MyDO"] },            // Create SQLite (recommended)
    // { "tag": "v1", "new_classes": ["MyDO"] },                // Create KV (paid only)
    { "tag": "v2", "renamed_classes": [{ "from": "Old", "to": "New" }] },
    { "tag": "v3", "transferred_classes": [{ "from": "Src", "from_script": "old", "to": "Dest" }] },
    { "tag": "v4", "deleted_classes": ["Obsolete"] }           // Destroys ALL data!
  ]
}
```

**Migration rules:**
- Tags must be unique and sequential (v1, v2, v3...)
- No rollback supported (test with `--dry-run` first)
- Auto-applied on deploy
- `new_sqlite_classes` recommended over `new_classes` (SQLite vs KV)
- `deleted_classes` immediately destroys ALL data (irreversible)

## Environment Isolation

Separate DO namespaces per environment (staging/production have distinct object instances):

```jsonc
{
  "durable_objects": {
    "bindings": [{ "name": "MY_DO", "class_name": "MyDO" }]
  },
  "env": {
    "production": {
      "durable_objects": {
        "bindings": [
          { "name": "MY_DO", "class_name": "MyDO", "environment": "production" }
        ]
      }
    }
  }
}
```

Deploy: `npx wrangler deploy --env production`

## Limits & Settings

```jsonc
{
  "limits": { 
    "cpu_ms": 300000  // Max CPU time: 30s default, 300s max
  }
}
```

See [Gotchas](./gotchas.md) for complete limits table.

## Types

```typescript
import { DurableObject } from "cloudflare:workers";

interface Env {
  MY_DO: DurableObjectNamespace<MyDO>;
}

export class MyDO extends DurableObject<Env> {}

type DurableObjectNamespace<T> = {
  newUniqueId(options?: { jurisdiction?: string }): DurableObjectId;
  idFromName(name: string): DurableObjectId;
  idFromString(id: string): DurableObjectId;
  get(id: DurableObjectId): DurableObjectStub<T>;
};
```

## Commands

```bash
# Development
npx wrangler dev                    # Local dev
npx wrangler dev --remote           # Test against production DOs

# Deployment
npx wrangler deploy                 # Deploy + auto-apply migrations
npx wrangler deploy --dry-run       # Validate migrations without deploying
npx wrangler deploy --env production

# Management
npx wrangler durable-objects list                      # List namespaces
npx wrangler durable-objects info <namespace> <id>     # Inspect specific DO
npx wrangler durable-objects delete <namespace> <id>   # Delete DO (destroys data)
```

## See Also

- **[API](./api.md)** - DurableObjectState and lifecycle handlers
- **[Patterns](./patterns.md)** - Multi-environment patterns
- **[Gotchas](./gotchas.md)** - Migration caveats, limits