Resource

A Resource represents a cloud entity managed by Alchemy — a bucket, database, queue, function, DNS record, or anything else that has a lifecycle of create, update, and delete.

Declaring a Resource

Resources are declared with a logical ID and optional input properties:

const bucket = yield * Cloudflare.R2Bucket("Bucket");
const queue =
  yield *
  AWS.SQS.Queue("Jobs", {
    fifoQueue: true,
  });

The logical ID ("Bucket", "Jobs") is stable across deploys. It identifies this resource within the stack and is used to track state.

Input Properties and Output Attributes

Every resource has two sides:

• Input Properties — the desired configuration you pass in (e.g. fifoQueue: true)
• Output Attributes — the values produced after creation (e.g. queueUrl, queueArn)

Output attributes are available as Output expressions on the resource:

const bucket = yield * Cloudflare.R2Bucket("Bucket");
bucket.bucketName; // Output<string>

These are lazy references that resolve after the resource is created. You can pass them as inputs to other resources to express dependencies.

Resources are Effects

A resource declaration like Cloudflare.R2Bucket("Bucket") is just an Effect — it doesn’t execute anything on its own. It only runs when you yield* it inside a Stack.

This means you can declare resources in separate files and import them freely:

src/bucket.ts

export const Bucket = Cloudflare.R2Bucket("Bucket");

// src/worker.ts
import { Bucket } from "./bucket.ts";
const bucket = yield * Cloudflare.R2Bucket.bind(Bucket);

Importing a resource from multiple files is safe — it registers on the stack exactly once (keyed by its fully qualified name).

Physical Names

Each resource gets a physical name generated from the stack name, stage, and logical ID (e.g. myapp-dev-bucket-abc123). The suffix is deterministic, derived from the resource’s instance ID.

Physical names ensure:

• Resources in different stages don’t collide
• Creates are idempotent (same inputs → same physical name)
• Resources can be recovered after state persistence failures

Replacement

When a property change requires replacing a resource (rather than updating in-place), Alchemy:

1. Creates a new resource with a new instance ID
2. Updates downstream resources to reference the new one
3. Deletes the old resource

The resource’s provider determines which property changes trigger replacement vs in-place update.