DuckDB has introduced Quack, a new client-server protocol enabling database instances to communicate directly. This breakthrough allows multiple concurrent writers to access the same database file, overcoming a significant limitation of DuckDB's traditional in-process architecture. The protocol builds on proven HTTP technology, making it familiar and efficient for developers while maintaining DuckDB's characteristic simplicity and ease of setup.

Quack operates through a request-response pattern using the application/duckdb MIME type for serialization. Available in DuckDB v1.5.2, the extension allows DuckDB to function as both client and server across different machines or processes. Authentication uses tokens, and the protocol supports both complex queries and large datasets through its efficient implementation leveraging DuckDB's internal serialization primitives.

The introduction of Quack addresses numerous workarounds users had developed for multi-process access to DuckDB databases. By embracing client-server architecture while maintaining its in-process capabilities, DuckDB expands its utility as a universal data wrangling tool without compromising its core design principles. This development represents a pragmatic evolution for a database system that has remained true to its philosophy while adapting to broader use cases.