OpenDuck brings MotherDuck's cloud database innovations to open-source, enabling transparent hybrid execution and differential storage for DuckDB. The project reimplements key architectural concepts - differential storage via append-only layers with PostgreSQL metadata, dual execution with split query plans, and a minimal gRPC protocol - while maintaining DuckDB's native integration. Developers can now self-host cloud-native database capabilities using gRPC + Arrow IPC for cross-system communication.

The system architecture splits queries between local machines and remote workers through an OpenDuckCatalog interface. A Rust gateway handles plan splitting and backpressure management, while embedded DuckDB workers execute local operations. Remote tables appear as first-class catalog entries, participating in JOINs and CTEs like native tables. The two-RPC protocol (execution and result streaming) ensures compatibility with any Arrow-supporting backend, from the included Rust gateway to custom implementations.

Unlike MotherDuck's proprietary cloud service, OpenDuck offers full transparency with its MIT-licensed codebase. It maintains DuckDB's extension model while introducing new storage mechanisms - sealed layers in object storage with consistent snapshots. The project includes Python and CLI tools for quick adoption, with Docker support for the gateway service. Technical details reveal a modular design separating authentication, routing, and execution.

OpenDuck differs fundamentally from Arrow Flight SQL by focusing exclusively on DuckDB integration rather than generic database protocols. While Arrow Flight offers broader compatibility, OpenDuck's deeper DuckDB optimization enables native query planning across local and remote resources. The project acknowledges MotherDuck's pioneering work while establishing its own open-source identity.