If the simulator is running slowly or failing to fetch personalized results for the selected user, the issue may be related to the facets selected in your Personalization strategy.
If the selected facets have too many unique values, for example SKU or objectID, it can significantly slow down the simulator's retrieval process and potentially cause it to timeout. In addition to this, facets with too many unique values are also unlikely to produce any meaningful affinities.
To improve the simulator's performance, and also get more relevant personalized results for users, we recommend using facets with values shared between multiple records such as categorical attributes like category or color.
You can read more about what makes a good facet choice here.