How can I release app data after logging off?

My team and I are developing an app which involves session login, downloading a bunch of information from some WS and after the users day operation, a log off is required. But we`ve recently noticed that after several days using the application, de app data is always increasing, even though we clean IndexedDB before any login!

Can someone give me any tip of what to do?

After 6 days using the app, the app data increased to 20Mb and app went awfully slow, making operation impossible.

Best regards, thanks in advance!