Joining cobk and coep table using Inner join taking too long

You can make use of T-Code: SE11 to check what indexes are available for table COEP

For one COEP record that you have the (now) 5 criteria for, navigate to T-Code: SE16 pass the selections and run to check how long it takes.

To improve performance, you can also create an additional index in table COEP. You can also run a SQL trace in ST05 to see what indexes are used and if indexes are not improving performance.