# Migrate CloudFront distribution: Downloadable file delivery

## Summary

Move CDN delivery from CloudFront distribution to Ample, one component at a time. Destination verified on Ample: a generated CSV stored with a Content-Disposition attachment header and served from the CDN URL with that header intact, so browsers download it under the stored filename. Source procedure: Record the distribution's origins, cache behaviors, TTLs and the object keys the app references. Not migrated automatically: CloudFront cache behaviors, Lambda@Edge and CloudFront Functions, signed URLs and custom TTLs are not migrated; Ample verifies delivery of published bucket objects only. Cutover: Redeploy the app with the new asset base URL, verify delivery from the CDN URL, keep the distribution until confirmed, then disable it. Rollback: keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

## Infrastructure requirements

- [CDN](/discover/primitive/cdn): verified (The CDN host serves objects from published buckets. It does not front app compute and is not a cache or key-value store.)

## Prerequisites

- Authorized access to the CloudFront distribution 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, buckets:write

## 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 CloudFront distribution provides beyond the component you are moving. Out of scope here: CloudFront cache behaviors, Lambda@Edge and CloudFront Functions, signed URLs and custom TTLs are not migrated; Ample verifies delivery of published bucket objects only.
2. **Source step 1.** Record the distribution's origins, cache behaviors, TTLs and the object keys the app references.
3. **Source step 2.** Copy the public assets into a published Ample bucket under versioned keys with immutable Cache-Control.
4. **Source step 3.** Update the app to build asset URLs from the Ample public URL.
5. **Publish the destination bucket.** Create and publish the asset bucket, upload versioned assets with immutable Cache-Control, and point the app at the public URL.

```
   ample bucket publish <bucket-name>
   ```
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/downloadable-file-delivery).
7. **Cut over.** Redeploy the app with the new asset base URL, verify delivery from the CDN URL, keep the distribution until confirmed, then disable it.
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

- **Next.js pattern fixture (destination)** (tests/deploy-canaries/next-js-patterns): Verified destination basis: downloadable file delivery.

## Success checks

- destination app responds on its public URL (`/` on the live URL, expect ample canary next js patterns)
- downloadable-file-delivery check from the destination example (`/p/downloadable-file-delivery` 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 CloudFront distribution'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: CloudFront cache behaviors, Lambda@Edge and CloudFront Functions, signed URLs and custom TTLs are not migrated; Ample verifies delivery of published bucket objects only.
- Verified on the node-22 template at s-1vcpu-1gb; region, compliance and request-duration limits are unknown.
- PutObject and GetObject with path-style addressing are verified; bulk copy tooling and other S3 operations are not.

## Cost estimate

Estimated 5.00 USD per month (size prices from pricing.toml at build revision a1b8c38919e59cd035ebabaced73cf84ece24371).
- app server 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 Next.js pattern fixture deployed on Ample (next build then next start -H 0.0.0.0 -p $PORT on the node-22 template) and its checks passed (a generated CSV stored with a Content-Disposition attachment header and served from the CDN URL with that header intact, so browsers download it under the stored filename). The source-side export from CloudFront distribution 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.