Migrate Heroku app: Express

Summary

Move Express 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 <app> 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: verified (Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.)
• Postgres: verified (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

Exact tested configuration

• template: node-22
• runtime: node
• size: s-1vcpu-1gb
• install: npm install
• build: npm run build --if-present
• start: npm run start

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 <app> 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. npm install, npm run build --if-present, npm run start on the node-22 template. Pass the exported variables with --env; keep the source running.

   ample deploy . --name <app-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.

Tested examples

• Express pattern fixture (destination) (tests/deploy-canaries/express-patterns): Verified destination basis: Express compute.

Success checks

• destination app responds on its public URL (/ on the live URL, expect ample canary express patterns)
• configuration-secrets check from the destination example (/p/configuration-secrets on the live URL, expect see the pattern fixture checks)
• relational-records check from the destination example (/p/relational-records on the live URL, expect see the pattern fixture checks)
• 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

Estimated 10.00 USD per month (size prices from pricing.toml at build revision a1b8c38919e59cd035ebabaced73cf84ece24371).

• app server x1 s-1vcpu-1gb: 5.00 USD
• managed PostgreSQL database x1 s-1vcpu-1gb: 5.00 USD

Destination always-on monthly price of the tested sizes; apps auto-pause when idle. Source costs are unknown to Ample.

Verification evidence

• canary_run on 2026-09-21T02:34:39Z at revision 1d28ae0-dirty (CLI 0.1.21): Destination side verified: the Express pattern fixture deployed on Ample (npm install, npm run build --if-present, npm run start on the node-22 template) and its checks passed (the app built, started and answered on its public HTTPS URL with encrypted configuration delivered). The source-side export from Heroku app is documented from the vendor's standard tooling and was not executed by this catalog's evidence. (expires 2027-03-20T02:34:39Z)

Execution binding

No execution binding. This recipe is documentation only; nothing is executed automatically.