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Database / DuckDB Interview questions

What is the difference between DuckDB's in-process mode and its new client-server (Quack) protocol?

DuckDB's traditional, and still default, mode is fully in-process: the database engine is a library loaded directly inside the calling application, with no network protocol or separate server involved at all. The newer Quack protocol adds an optional, genuine client-server deployment mode on top of DuckDB, letting a DuckDB instance run as a standalone, network-accessible service that separate client processes (potentially on different machines) connect to.

In-process (traditional)Quack client-server
Database engine runs inside the calling application's process.Database runs as a separate, network-accessible service.
No authentication/authorization layer needed for local access.Includes an OAuth/OIDC authentication layer for controlled access.
Best for single-process, embedded use cases.Best for deployable, shared analytical services accessed by multiple clients.

This addition doesn't replace DuckDB's embedded model, it extends DuckDB's applicability to a genuinely different deployment pattern: a shared, centrally-hosted DuckDB service that multiple applications or users can connect to over a network, with proper authentication, something the traditional embedded model was never designed to support on its own.

The Quack protocol adds to DuckDB the ability to:
The Quack protocol includes which security-related feature?

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