clover's git

the-knife

1	---
2	title: Regions
3	description: Where Fly Machines, Volumes, Postgres, and Redis live. Alchemy defaults to iad.
4	---
5
6	A region is a Fly.io datacenter. [Machines](/fly/compute/machines),
7	[Volumes](/fly/data/volumes), [Postgres](/fly/data/postgres)
8	clusters, and a [Redis](/fly/data/redis) primary live in one. An
9	[App](/fly/compute/apps) is global. It is not pinned to a region.
10
11	Alchemy defaults to `iad` (Ashburn, Virginia). Pass `region` to put
12	a [Service](/fly/compute/services), Machine, or Postgres cluster
13	somewhere else.
14
15	## Pin a Service
16
17	```typescript
18	export default class Api extends Fly.Service<Api>()(
19	"Api",
20	{ main: import.meta.url, region: "lhr", port: 3000 },
21	Effect.gen(function* () {
22	return {
23	fetch: Effect.succeed(HttpServerResponse.text("hello")),
24	};
25	}),
26	) {}
27	```
28
29	`count` Machines run in that region.
30
31	:::caution[Changing `region` moves the Machines]
32	The Service keeps its App and hostname. Machines are created in the
33	new region and the old ones are deleted. A Volume does not move with
34	them.
35	:::
36
37	## Pin a Machine
38
39	```typescript
40	const web = yield* Fly.Machine("Web", {
41	app: Site,
42	region: "syd",
43	image: "nginx:alpine",
44	});
45	```
46
47	Each Machine resource is one VM in one region. To run in two
48	regions, declare two Machines.
49
50	:::caution[Changing `region` replaces the Machine]
51	The Machine is created in the new region. The old one is deleted.
52	:::
53
54	## Volumes stay in the region
55
56	A Volume is created in the parent Service or Machine's region. It
57	cannot move and cannot attach to a Machine in another region.
58
59	Restore into a new region from a
60	[`VolumeSnapshot`](/providers/fly/volumesnapshot) with `snapshotId`
61	on the mount.
62
63	## Several regions, one hostname
64
65	Pass a list to `region` to run the same Service in several regions
66	behind one hostname. `count` Machines run in each region, and Fly's
67	Anycast proxy sends each request to the nearest healthy Machine.
68
69	```typescript
70	export default class Api extends Fly.Service<Api>()(
71	"Api",
72	{ main: import.meta.url, region: ["iad", "lhr"], count: 2 },
73	Effect.gen(function* () {
74	return {
75	fetch: Effect.succeed(HttpServerResponse.text("hello")),
76	};
77	}),
78	) {}
79	```
80
81	This runs four Machines: two in `iad` and two in `lhr`. `api.regions`
82	is `["iad", "lhr"]`, and `api.url` serves from both.
83
84	Adding or removing a region updates the Service in place. Its App and
85	hostname stay the same, Machines in regions you keep are left alone,
86	and a removed region's Machines are deleted. A Volume from
87	`MountVolume` is created in each Machine's own region.
88
89	## Which region is this?
90
91	Fly sets `FLY_REGION` on the Machine. Read it in a Service with
92	`Config`.
93
94	```typescript
95	import * as Config from "effect/Config";
96
97	const region = yield* Config.String("FLY_REGION");
98	```
99
100	## Region codes
101
102	Codes are three letters. This list is what Fly published as of
103	August 2026. Run `fly platform regions` or see
104	[Fly's regions](https://fly.io/docs/reference/regions/) for the
105	live set.
106
107	| Code | Location |
108	| --- | --- |
109	| `ams` | Amsterdam, Netherlands |
110	| `arn` | Stockholm, Sweden |
111	| `bom` | Mumbai, India |
112	| `cdg` | Paris, France |
113	| `dfw` | Dallas, Texas (US) |
114	| `ewr` | Secaucus, NJ (US) |
115	| `fra` | Frankfurt, Germany |
116	| `gru` | São Paulo, Brazil |
117	| `iad` | Ashburn, Virginia (US) |
118	| `jnb` | Johannesburg, South Africa |
119	| `lax` | Los Angeles, California (US) |
120	| `lhr` | London, United Kingdom |
121	| `nrt` | Tokyo, Japan |
122	| `ord` | Chicago, Illinois (US) |
123	| `sin` | Singapore |
124	| `sjc` | San Jose, California (US) |
125	| `syd` | Sydney, Australia |
126	| `yyz` | Toronto, Canada |
127
128	A dedicated [`IpAssignment`](/fly/networking) can take `region`
129	too. Shared Anycast (`shared_v4`) ignores it.
130
131	## Postgres is regional
132
133	The cluster lives in one region. Pass `region` on
134	[`Fly.Postgres`](/fly/data/postgres), not on the App.
135
136	```typescript
137	const db = yield* Fly.Postgres("Db", {
138	region: "iad",
139	});
140	```
141
142	:::caution[Changing `region` replaces the cluster]
143	A new cluster is created in the new region. The old cluster is
144	deleted. Data is not copied.
145	:::
146
147	## Redis primary
148
149	[`Fly.Redis`](/fly/data/redis) takes `primaryRegion`. Default is
150	`iad`. Read replicas are extra regions on `readRegions`.
151
152	```typescript
153	const cache = yield* Fly.Redis("Cache", {
154	primaryRegion: "iad",
155	readRegions: ["sjc"],
156	});
157	```
158
159	:::caution[Changing `primaryRegion` replaces Redis]
160	The primary region is immutable. The old database is deleted first.
161	:::
162
163	## Where next
164
165	[Services](/fly/compute/services) pin `region` on the class.
166	[Machines](/fly/compute/machines) pin it on the resource.
167	[Volumes](/fly/data/volumes) follow the parent.
168	[Postgres](/fly/data/postgres) is a billed cluster in one region.
169	[Redis](/fly/data/redis) pins `primaryRegion`.