1# DO Storage Configuration
2 
3## SQLite-backed (Recommended)
4 
5**wrangler.jsonc:**
6```jsonc
7{
8  "migrations": [
9    {
10      "tag": "v1",
11      "new_sqlite_classes": ["Counter", "Session", "RateLimiter"]
12    }
13  ]
14}
15```
16 
17**Migration lifecycle:** Migrations run once per deployment. Existing DO instances get new storage backend on next invocation. Renaming/removing classes requires `renamed_classes` or `deleted_classes` entries.
18 
19## KV-backed (Legacy)
20 
21**wrangler.jsonc:**
22```jsonc
23{
24  "migrations": [
25    {
26      "tag": "v1",
27      "new_classes": ["OldCounter"]
28    }
29  ]
30}
31```
32 
33## TypeScript Setup
34 
35```typescript
36export class MyDurableObject extends DurableObject {
37  sql: SqlStorage;
38  
39  constructor(ctx: DurableObjectState, env: Env) {
40    super(ctx, env);
41    this.sql = ctx.storage.sql;
42    
43    // Initialize schema
44    this.sql.exec(`
45      CREATE TABLE IF NOT EXISTS users(
46        id INTEGER PRIMARY KEY,
47        name TEXT NOT NULL,
48        email TEXT UNIQUE
49      );
50    `);
51  }
52}
53 
54// Binding
55interface Env {
56  MY_DO: DurableObjectNamespace;
57}
58 
59export default {
60  async fetch(request: Request, env: Env): Promise<Response> {
61    const id = env.MY_DO.idFromName('singleton');
62    const stub = env.MY_DO.get(id);
63    
64    // Modern RPC: call methods directly (recommended)
65    const result = await stub.someMethod();
66    return Response.json(result);
67    
68    // Legacy: forward request (still works)
69    // return stub.fetch(request);
70  }
71}
72```
73 
74## CPU Limits
75 
76```jsonc
77{
78  "limits": {
79    "cpu_ms": 300000  // 5 minutes (default 30s)
80  }
81}
82```
83 
84## Location Control
85 
86```typescript
87// Jurisdiction (GDPR/FedRAMP)
88const euNamespace = env.MY_DO.jurisdiction("eu");
89const id = euNamespace.newUniqueId();
90const stub = euNamespace.get(id);
91 
92// Location hint (best effort)
93const stub = env.MY_DO.get(id, { locationHint: "enam" });
94// Hints: wnam, enam, sam, weur, eeur, apac, oc, afr, me
95```
96 
97## Initialization
98 
99```typescript
100export class Counter extends DurableObject {
101  value: number;
102  
103  constructor(ctx: DurableObjectState, env: Env) {
104    super(ctx, env);
105    
106    // Block concurrent requests during init
107    ctx.blockConcurrencyWhile(async () => {
108      this.value = (await ctx.storage.get("value")) || 0;
109    });
110  }
111}
112```
113