Statsig

Experiments and their groups, gates and their rules, the exposure events Statsig logs, the metric definitions in the customer's metrics catalogue, and the ID types a unit is assigned on.

Nothing on the first rung. Once the rung permits it, an experiment or a gate with its allocation, created new, never a change to one the customer's code already reads.

Statsig's own assignment: the SDK in the customer's product assigns the unit and logs the exposure, and Athren reads that exposure, so the arms Athren compares are the arms Statsig served.

The customer's events as logged to Statsig, joined to the exposure, and the downstream business metric defined in Athren with the window the experiment states; Statsig's own pulse results are read where the customer has them.

A console API key with read access; the experiment write is requested only when the rung that uses it is on, and it is the only write.

The gate off or the experiment stopped, which returns every unit to the control arm; the change versioned in Athren with who approved it and when.