### Migrate Google Cloud SQL for PostgreSQL: Durable job state

Move PostgreSQL data from Google Cloud SQL for PostgreSQL to Ample, one component at a time. Destination verified on Ample: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true).

#### Source procedure:
Take a logical backup with `pg_dump -Fc` through the Cloud SQL Auth Proxy or an authorized network.

##### Not migrated automatically:
Cloud SQL Auth Proxy/IAM authentication, high availability and PITR have no equivalent on the managed database.

#### Cutover:
Freeze writes with the user's go-ahead, take the final dump, restore, validate, redeploy with the managed DATABASE_URL, keep Cloud SQL until confirmed.

#### Rollback:
Keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

### Workflow Steps
1. **Inventory the source**: List what Google Cloud SQL for PostgreSQL provides beyond the component you are moving. Out of scope here: Cloud SQL Auth Proxy/IAM authentication, high availability and PITR have no equivalent on the managed database.
2. **Source step 1**: Take a logical backup with `pg_dump -Fc` through the Cloud SQL Auth Proxy or an authorized network.
3. **Source step 2**: Check the engine major version, extensions, and flags the app depends on.
4. **Source step 3**: Restore into a scratch managed database first and compare row counts.
5. **Provision and restore**: Deploy the app once so a managed PostgreSQL 16 database exists (or create one with `ample database create --engine postgres`), then restore the dump with pg_restore using its connection string; keep migrations idempotent.
6. **Validate before cutover**: Run the app's own checks and, for data, compare counts and checksums; the example checks are the pattern self-tests (/p/durable-job-state).
7. **Cut over**: Freeze writes with the user's go-ahead, take the final dump, restore, validate, redeploy with the managed DATABASE_URL, keep Cloud SQL until confirmed.
8. **Rollback**: Point DNS or configuration back to the source. The source was never modified; deletion is a separate, user-executed step after validation.

### Prerequisites
- Authorized access to the Google Cloud SQL for PostgreSQL source and its export tooling.
- An inventory of every component in scope and out of scope.
- A validated backup or copy before any cutover.
- An Ample account token with servers:write, databases:read.

### Tested Configuration
- **Template**: node-22
- **Runtime**: node
- **Size**: s-1vcpu-1gb
- **Install**: npm install
- **Build**: npm run build --if-present
- **Start**: npm run start

### Limitations
- Documentation only: nothing is executed automatically, and no execution binding is offered.
- The source-side procedure is documented from Google Cloud SQL for PostgreSQL's standard tooling and was not executed in this catalog's evidence; the destination side was verified with the pattern fixture.
- No full source-product parity is claimed: Cloud SQL Auth Proxy/IAM authentication, high availability and PITR have no equivalent on the managed database.
- Verified on the node-22 template at s-1vcpu-1gb; region, compliance, and request-duration limits are unknown.
- Managed PostgreSQL 16 only; extensions, connection limits, and backup or restore procedures on the managed side are not verified beyond the pattern checks.