Jumbox
Private, local-first file transfer system with resumable streaming and end-to-end integrity.
The Challenge
Sharing files across the same LAN or Wi-Fi still usually means routing them through a third-party cloud service, and once a large transfer starts, a dropped connection means starting over from zero — there's no direct, private way to just push files from one machine on the network to another with resilience built in.
Engineering Delivery
Built Jumbox as a self-hosted FastAPI service with a layered domain model (a TransferSession aggregate managing TransferItem entities), exposing multi-file transfer sessions under an 8-digit share code or QR code that other devices on the LAN can pick up. Uploads use a resumable chunk protocol (PATCH .../chunks with Upload-Offset probing) that survives network drops without retransmitting already-accepted bytes, backed by automatic retries with exponential backoff. Every transfer is verified end-to-end via SHA-256 with checksum and ETag headers, downloads stream directly to disk with Accept-Ranges support to avoid buffering large files in memory, and an optional ephemeral mode purges files from disk the moment the recipient downloads them. Runs zero-config on SQLite for standalone use or Postgres via Docker Compose for a production stack, with SQLAlchemy 2.0 and Alembic migrations underneath.