We have inherited a legacy system where the tokens are generated by an external application. They are imported directly via SQL into the Limesurvey token table instead of using the API.
We would like to ensure the uniqueness of the tokens with a unique constraint on the token columns in the token table.
Has anybody done something like this or has any knowledge if this could affect the Limesurvey application negatively in any way?

Your LimeSurvey version ?

There are an issue in 4.X, not in 3.X

The version is 2.50.

2.50 … version to old and with a lot of issue …