The ReadListener itself doesn't perform the database query. It delegates the work to a Data Provider. The slow performance you observed is because the data provider, during the hydration phase, is likely executing multiple additional queries (the N+1 problem) to load related associations. This happens after the initial main query, leading to the high time spent in the listener.

The ReadListener's role is simply to orchestrate this process and make the retrieved data available to the rest of the framework. The heavy lifting—and the source of your performance problem—lies with the underlying data provider implementation and how it fetches the data.