CloudTranscode is a PHP-based distributed media transcoding pipeline built around AWS Step Functions. It runs as long-polling activity workers that register against SFN activities, fetch JSON payloads describing an input asset (an S3 object or HTTP URL) and a list of desired output assets, then execute FFmpeg for video/thumbnails or ImageMagick for images, upload the results to S3, and report progress via heartbeats and client callbacks. The two primary entry points are ValidateAssetActivity, which probes an asset's MIME type and metadata using only the first 1 KiB of data and ffprobe, and TranscodeAssetActivity, which processes all output_assets sequentially and dispatches each to a media-type-specific transcoder. Workers are stateless Docker containers designed to run on ECS and scale horizontally by polling distinct SFN activity ARNs.