# Migrate Heroku app: Next.js

## Summary
Move Next.js compute from Heroku app to Ample, one component at a time. Destination verified on Ample: the app built, started and answered on its public HTTPS URL with encrypted configuration delivered.  
Source procedure: Export config vars with `heroku config -s -a ` into an env file kept out of the repository.  
Not migrated automatically: Heroku add-ons other than Postgres, release-phase scheduling, dyno autoscaling and Heroku Scheduler are not migrated; use `--release-command` for release tasks.  
**Cutover**: Add the custom domain with `ample domain add`, update DNS from the Heroku DNS target, keep the Heroku app until verified, then scale it down.  
**Rollback**: keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

## Infrastructure Requirements
### Compute
- **Label**: Compute  
- **Status**: verified  
- **Summary**: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.

### Postgres
- **Label**: Postgres  
- **Status**: verified  
- **Summary**: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.

## Prerequisites
- Authorized access to the Heroku app 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

## Workflow Steps
1. **Inventory the source**  
   List what Heroku app provides beyond the component you are moving. Out of scope here: Heroku add-ons other than Postgres, release-phase scheduling, dyno autoscaling and Heroku Scheduler are not migrated; use `--release-command` for release tasks.
2. **Source step 1**  
   Export config vars with `heroku config -s -a ` into an env file kept out of the repository.
3. **Source step 2**  
   Translate the `Procfile` web process into the start command (`--start` or the package manifest's start script); worker processes need a separate `--kind worker` service.
4. **Source step 3**  
   Note buildpacks and add-ons in use; managed databases replace Heroku Postgres, other add-ons need their own plan.
5. **Deploy on Ample in parallel**  
   `next build` then `next start -H 0.0.0.0 -p $PORT` on the node-22 template. Pass the exported variables with `--env`; keep the source running.
   Command: `ample deploy . --name  --public --env-file .env.production`
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/configuration-secrets`, `/p/relational-records`).
7. **Cut over**  
   Add the custom domain with `ample domain add`, update DNS from the Heroku DNS target, keep the Heroku app until verified, then scale it down.
8. **Rollback**  
   Point DNS or configuration back to the source. The source was never modified; deletion is a separate, user-executed step after validation.

## Success Checks
- **destination app responds on its public URL**  
- **configuration-secrets check from the destination example**
- **relational-records check from the destination example**
- **data or object counts and checksums match the source**

## Limitations
- Documentation only: nothing is executed automatically and no execution binding is offered.
- The source-side procedure is documented from Heroku app'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: Heroku add-ons other than Postgres, release-phase scheduling, dyno autoscaling and Heroku Scheduler are not migrated; use `--release-command` for release tasks.
- 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.

## Cost Estimate
**Currency**: USD  
**Monthly Amount**: 10.0  
**Note**: Destination always-on monthly price of the tested sizes; apps auto-pause when idle. Source costs are unknown to Ample.  
- **App server**:  
  - **Size**: s-1vcpu-1gb  
  - **Quantity**: 1.0  
  - **Monthly Amount**: 5.0  
- **Managed PostgreSQL database**:  
  - **Size**: s-1vcpu-1gb  
  - **Quantity**: 1.0  
  - **Monthly Amount**: 5.0