## Host mobile backend with Axum: stored input and output artifacts

### Summary
Deploy a mobile backend built with Axum on Ample using the generated downloads pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, a managed PostgreSQL 16 database is auto-provisioned and injected as DATABASE_URL, a private S3-compatible bucket holds objects with credentials delivered as encrypted environment variables. Verified on Axum: an export query rendered to a CSV artifact stored with metadata in a private bucket and returned only to an authorized caller (401 without token, export=ok rows=3). Not separately tested: your export formats, retention policy and entitlement model; treat the mobile backend-specific behavior as your application code.

### Representative Queries
- Host mobile backend with Axum: stored input and output artifacts
- Where can I host Mobile backend built with Axum?
- I need an input/output artifact contract, object metadata and access boundaries.

### Resource Requirements
- **Compute**
- **Postgres**
- **S3-compatible object storage**

### Infrastructure Requirements
- **Compute**: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request.
- **Postgres**: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.
- **S3-compatible object storage**: Buckets are S3-compatible with issued credentials; PutObject and GetObject are verified by canary.

### Prerequisites
- An Axum project that builds and starts with the documented commands (cargo build --release in the rust builder image (stable toolchain, Cargo.lock committed, pure-Rust dependencies), then the release binary on the ubuntu-24.04 template reading PORT and DATABASE_URL).
- A PostgreSQL driver reading DATABASE_URL at runtime.
- A bucket from `ample bucket create` with its credentials passed as encrypted S3_* environment variables.
- An Ample account token with servers:write, databases:read, buckets:read.

### Workflow Steps
1. **Build and start**: `cargo build --release` in the rust builder image (stable toolchain, Cargo.lock committed, pure-Rust dependencies), then the release binary on the ubuntu-24.04 template reading PORT and DATABASE_URL. The server must bind 0.0.0.0 on PORT.
2. **Implement the pattern on PostgreSQL**: The fixture's module implements generated downloads: an export query rendered to a CSV artifact stored with metadata in a private bucket and returned only to an authorized caller.
3. **Wire object storage**: Create the bucket(s) and pass endpoint, region, bucket and keys as --env values.
4. **Deploy**: Run the synchronous deploy once and read the result.
5. **Verify**: Fetch the live URL and the pattern self-test route(s) from the example; then run your own checks.

### Success Checks
- App responds on its public URL.
- Generated-downloads self-test.

### Limitations
- Verified on the ubuntu-24.04 template with the example fixture.
- The mobile backend itself has not been separately tested; the pattern checks are what was verified.

### Cost Estimate
- **Monthly Amount**: $10.00
- **Components**:
  - App Server: $5.00
  - Managed PostgreSQL Database: $5.00

### Examples
- **Axum pattern fixture**: Multi-pattern Axum app whose generated downloads module was checked live.

### Next Actions
- Browse the catalog index.
- Search published recipes by intent, stack and constraints.
- Prepare a side-effect-free deployment plan for an authorized project.