# Deliver public assets through CDN for Phoenix

## Summary

Cdn assets for a Phoenix app on Ample. Verified on Phoenix: a versioned, immutable-cached asset uploaded to a published bucket and served from the CDN URL. Build and start: mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs.

## 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.)
- 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

- A Phoenix project (mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs)
- A bucket from `ample bucket create` with credentials passed as encrypted S3_* environment variables
- An Ample account token with servers:write, buckets:read

## Exact tested configuration

- template: `elixir-1.18`
- runtime: `elixir`
- size: `s-1vcpu-1gb`
- install: `mix local.hex --force && mix local.rebar --force && MIX_ENV=prod mix deps.get --only prod`
- build: `MIX_ENV=prod mix compile && MIX_ENV=prod mix release --overwrite`
- start: `PHX_SERVER=true _build/prod/rel/$(ls _build/prod/rel | head -n 1)/bin/$(ls _build/prod/rel | head -n 1) start`

## Steps

1. **Build and start.** mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs; the server must bind 0.0.0.0 on PORT.
2. **Publish a bucket for public assets.** Publish only the asset bucket; upload versioned keys with an immutable Cache-Control header and build URLs from its public URL.

```
   ample bucket publish <bucket-name>
   ```
3. **Verify.** Fetch the live URL and /p/versioned-static-assets on the example; on failure read the build and runtime logs.

```
   ample logs <deployment_id> --kind build
   ```

## Tested examples

- **Phoenix pattern fixture** (tests/deploy-canaries/phoenix-patterns): Verified CDN assets on Phoenix.

## Success checks

- app responds on its public URL (`/` on the live URL, expect ample canary phoenix patterns)
- versioned-static-assets check from the example (`/p/versioned-static-assets` on the live URL, expect see the pattern fixture checks)

## Limitations

- Verified on the elixir-1.18 template at s-1vcpu-1gb; other sizes and Phoenix major versions are not verified.
- Region, compliance attestations and request-duration limits are unknown and not claimed.
- The CDN serves published-bucket objects only; cache rules, purge and TTL control are not verified.

## Cost estimate

Estimated 5.00 USD per month (size prices from pricing.toml at build revision a1b8c38919e59cd035ebabaced73cf84ece24371).

Always-on monthly price of the tested sizes; apps auto-pause when idle. Buckets are allocation-priced per quota and not included.

## Verification evidence

- canary_run on 2026-09-20T23:45:31Z at revision `4d1511e574302f3904b75088bd4048a0975218b3-dirty (CLI 0.1.21)`: Phoenix pattern fixture deployed on Ample (mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs); for this guide: a versioned, immutable-cached asset uploaded to a published bucket and served from the CDN URL. (expires 2027-03-19T23:45:31Z)

Last verified: 2026-09-20T23:45:31Z

## Execution binding

MCP tool `ample_deploy` (registry `mcp:ample_deploy`), schema hash `876465fce906da0c` observed 2026-09-21T03:19:59.461917+00:00 at revision `49962bcade4f`, binding state `current`, required scopes: servers:write, buckets:read.