---
title: Content Delivery Network (CDN) | Scenario Docs
---

# Overview

Scenario’s Content Delivery Network provides secure, signed access to your assets with real-time transformation capabilities. The CDN delivers images, 3D models, and videos with features including resizing, format conversion, and optimization.

**CDN Domain**: `cdn.cloud.scenario.com`

# URL Structure

## Path Patterns

| Pattern               | Purpose                                       | Access              |
| --------------------- | --------------------------------------------- | ------------------- |
| `/assets/*`           | Original asset files                          | Requires signed URL |
| `/assets-transform/*` | Transformed assets (resized, converted, etc.) | Requires signed URL |
| `/thumbnails/*`       | Asset thumbnails                              | Public              |

# Signed URLs

All asset URLs (except thumbnails) are signed for security and expire automatically.

## Expiration Policy

Signed URLs use a rolling expiration window optimized for caching:

| Date Range  | Expiration Date        |
| ----------- | ---------------------- |
| 1st - 7th   | 14th of same month     |
| 8th - 14th  | 21st of same month     |
| 15th - 21st | Last day of same month |
| 22nd - 31st | 7th of next month      |

**Minimum expiration**: 24 hours from generation

Signed URLs include signature parameters (`Policy`, `Signature`, `Key-Pair-Id`) that are automatically added by the API.

Never change the given signature query strings, it would result in an Access Denied Error.

# Asset Transformation

Transform assets on-the-fly using the `/assets-transform/{assetId}` endpoint with query parameters.

## Image Transformation Parameters

| Parameter    | Type              | Default | Values                                | Description                      |
| ------------ | ----------------- | ------- | ------------------------------------- | -------------------------------- |
| `width`      | integer \| “auto” | auto    | > 0                                   | Target width in pixels           |
| `height`     | integer \| “auto” | auto    | > 0                                   | Target height in pixels          |
| `quality`    | integer           | 100     | 1-100                                 | Compression quality              |
| `format`     | string            | origin  | See below                             | Output format                    |
| `fit`        | string            | cover   | cover, contain, fill, inside, outside | Resize mode                      |
| `rotate`     | integer           | 0       | 0-360                                 | Rotation in degrees              |
| `blur`       | integer           | 0       | 0-100                                 | Blur strength                    |
| `greyscale`  | boolean           | false   | true, false                           | Convert to greyscale             |
| `flatten`    | boolean           | false   | true, false                           | Remove transparency              |
| `background` | string            | ffffff  | Hex (no #)                            | Background color when flattening |

## Supported Formats

**Image Formats**:

- `jpeg` / `jpg` - JPEG
- `png` - PNG with transparency
- `webp` - Modern WebP format
- `avif` - Next-gen AVIF format
- `tiff` / `tif` - TIFF
- `origin` - Keep original format
- `auto` - Auto-select best format

**3D Model Formats**:

- `glb` - Binary glTF
- `obj` - Wavefront OBJ
- `fbx` - Autodesk FBX

## Resize Modes (fit parameter)

- **`cover`** (default) - Crop to fill dimensions, maintains aspect ratio
- **`contain`** - Scale to fit within dimensions, may add letterboxing
- **`fill`** - Stretch to exact dimensions, may distort
- **`inside`** - Scale down to fit within dimensions only
- **`outside`** - Scale to cover dimensions, may crop

![](https://files.readme.io/0bbf08d4a05014ff85f589c04f8434e06cf948aabd07436f5db6299e83387533-image.png)



## Example Transformations

```
# Resize to 512x512, convert to WebP
https://cdn.cloud.scenario.com/assets-transform/{assetId}?width=512&height=512&format=webp&quality=90&Policy=...&Signature=...&Key-Pair-Id=...


# Auto-width, 1024px height, maintain aspect ratio
https://cdn.cloud.scenario.com/assets-transform/{assetId}?height=1024&width=auto&fit=inside&Policy=...&Signature=...&Key-Pair-Id=...


# Convert to greyscale with slight blur
https://cdn.cloud.scenario.com/assets-transform/{assetId}?greyscale=true&blur=5&Policy=...&Signature=...&Key-Pair-Id=...


# Convert 3D model to GLB format
https://cdn.cloud.scenario.com/assets-transform/{assetId}?format=glb&Policy=...&Signature=...&Key-Pair-Id=...


# Flatten transparency with custom background
https://cdn.cloud.scenario.com/assets-transform/{assetId}?flatten=true&background=000000&Policy=...&Signature=...&Key-Pair-Id=...
```

# API Usage

## Get Asset Download URL

Generate a signed download URL with optional format conversion.

**Endpoint**: `POST /v1/assets/{assetId}/download`

**Request**:

```
{
  "targetFormat": "webp"  // Optional - any supported format
}
```

**Response**:

```
{
  "url": "https://cdn.cloud.scenario.com/assets-transform/{assetId}?format=webp&Policy=...&Signature=...&Key-Pair-Id=..."
}
```

## Asset Object URLs

When retrieving assets through the API (e.g., `GET /v1/assets`), the response includes a pre-signed `url` field:

```
{
  "assets": [{
    "id": "asset-id",
    "url": "https://cdn.cloud.scenario.com/assets-transform/{assetId}?...",
    ...
  }]
}
```

These URLs are already signed and ready to use.

# Caching

- **Transformed assets** are cached for faster subsequent access
- **Cache duration**: Up to 24 hours (respects signed URL expiration)
- **Cache key**: Based on asset ID and transformation parameters

For consistent cache hits, use the same transformation parameters. Varying parameters (e.g., `width=512` vs `width=513`) will create separate cache entries.

# Best Practices

## Performance

1. **Use WebP or AVIF** for modern browsers to reduce bandwidth
2. **Specify exact dimensions** when possible to optimize caching
3. **Set appropriate quality** (80-90 typically sufficient for web)
4. **Use `fit=inside`** to prevent upscaling small images

## Format Selection

- **PNG**: When transparency is required
- **JPEG**: For photos without transparency
- **WebP**: Best compression for modern browsers
- **AVIF**: Smallest file size, newer browser support
- **Auto**: Let the CDN choose based on browser support

## Dimensions

- **Thumbnails**: 256x256 or 512x512
- **Preview**: 1024px on longest side
- **Full quality**: 2048px or original size
- **Use `auto`** for one dimension to maintain aspect ratio