When a base table has multiple indices, the where clause should be in the order of the index, either a primary or a secondary index.
To choose an index, the optimizer checks the field names specified in the where clause and then uses an index that has the same order of the fields. One more tip is that if a table begins with MANDT, while an index does not, there is a high possibility that the optimizer might not use that index.
In certain scenarios, it is advisable to check whether a new index can speed up the performance of a program. This will come handy in programs that access data from the finance tables.