Consider Quack protocol

[derekperkins]

This was just released, so I felt it was worth having a discussion here, but I don't think it's production ready enough to put this into an issue. In the release post, they explicitly call out WASM support as a potential use case for this protocol. I've got a few thoughts about this:

1. If we decided to enable this, this would tie Mosaic more closely and tightly to DuckDB, which has the benefit of not requiring a Mosaic-specific server, but that also doesn't allow for any custom server side logic that you currently have access to in a Mosaic server.
2. There's another option that maybe this could be implemented next to REST and WebSocket as just another protocol. It would be slightly different because those at least share the same payloads, and this would bypass that and go straight to DuckDB. That might be an alternative that wouldn't require the Mosaic server for those who don't have advanced needs for it.

• https://duckdb.org/2026/05/12/quack-remote-protocol
• https://duckdb.org/quack/

Alternatively to server-side, this also might provide some options for cross-tab usage. Currently, DuckDB WASM doesn't allow to be run as a shared worker, which has some issues if you have multiple tabs trying to access the same OPFS or other data stores. Maybe this allows some client-server relationships to a shared worker? I'm not convinced that that would work, but maybe it's worth investigating?

[domoritz]

I've been thinking about how Quack could be used. The thing is for Mosaic we would only use it when there is a server with the data. In that case we would still need another DuckDB instance in the browser rather than just a library to process Arrow. We should check how much benefit we would get in terms of performance.

[derekperkins]

It could make for some interesting options for hybrid execution. Potentially some introspection on table sizes, and under a certain size you bring it all client side, otherwise do intermediate steps server side. They explicitly call out MotherDuck's custom protocol as inspiration, which I believe is primarily for this use case.

• Multi-tier Execution #389

[derekperkins]

Related issue

• Investigate quack #1116