Hard filtering rules need to be implemented in a RescorerProvider, or in logic on the caller side. Tagging users and items with a locale could make sense. It would function as a soft filter nudging people towards things in the same locale. That could be useful as well, but is a different thing from implementing business rules. If your items and users are nearly completely disjoint by locale (e.g. very few items are available in multiple locales and very few users shop in multiple locales) then separate models might be the best way to go. No filtering logic needed although you then manage a model per locale. But the models are smaller and easier to handle. If there is moderate overlap, then a unified model can benefit from the cross-locale learning. ... View more