Custom extractor performance issues

We have 1 custom extractor to pull Shipments and Deliveries data from VTTK, VTTP, LIKP, LIPS tables. There are reasons why went with custom instead of standard one.

Problem is with performance. We are trying to pull shipments and deliveries which are changed

in last 3 days or created in last 3 days. The extractor is damn slow. How do we improve performance.

1 option is to create indexes on created on and changed on date so that selects on tables is faster.

Is there any other option?