Context:

Once process instance indices are created per definition key, we can consider whether it is feasible to merge normal and event based process instances indices.

Currently, to avoid additional logic to determine if the required instance index is event based or not, we use an additional alias on event based process instance indices that resembles a non event based process instance index name. 

Merging them would also simplify version handling on process and event based process instance indices, as described in the backend senate. Alternatively, if merging the indices is not feasible, we could consider giving the event based process instance index its own version so it does not need reindexed for migrations that otherwise only affect the "normal" process instance index.

AT:

• If possible and sensible, merge process instance indices or alternatively, separate the version handling between the indices