Phoenix - return Ecto query results to a specific client

I'm currently trying to devise a scheme where the following happens.

Client A is subscribed/connected to topic/channel T.

A sends a message in the form of a select query to T.

Only A receives the query results, no other subscribers.

Is this even possible using Channels? The main reason I chose Channels was for the excellent websocket support - however I'm open to other Phoenix solutions.

Yes, Channels should do the work you want. You can push the query results down to the user who sent the query using push:

def handle_in("new_query", %{"query" => query}, socket) do

    # do the query and store the result into query_result

    #return back the result using push to the user
    push socket, "new_query", %{query_result: query_result}
    {:ok, socket}
end

If you want to return the query result to all users who are joined to the topic, you can simply use broadcast instead of push, see the docs here