Service order lookup in BSEG

Hello

I am trying to look up postings for a service order in table BSEG. Using service order (BSEG-AUFNR) is however very bad from performance perspective, it takes several minutes to look up the service order.

Is there any way to reduce the response time of this query? I have tried to look for links between the service order and entries in table BKPF, but without success.

BR,

OT