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Great question.

This is definitely a blind spot in the app. Because `timestamp` isn't a required field in the User Dimension definition, we have to use some arbitrary rule making to select one user dimension per user (right now we just use `MAX`).

On your end, the best way to handle this would be to define your User Dimension using <https://docs.growthbook.io/app/metrics#sql-templates|SQL Template variables > where you define your user dimension yourself to get the latest record per user that has a `timestamp &lt; {{startDate}}` so that you can ensure all dimensions are pre-experiment (best for bias).

You could do something like the following:

```WITH visitor_types AS (
SELECT
  anonymous_id,
  visitor_type,
  ROW_NUMBER() OVER (PARTITION BY anonymous_id ORDER BY timestamp DESC) AS rn
FROM
  dim_table
WHERE
  timestamp &gt; DATE_SUB({{startDate}}, INTERVAL 7 DAY) AND timestamp &lt; {{startDate}}
)

SELECT
  anonymous_id,
  visitor_type
FROM visitor_types
WHERE rn = 1
  ```