Very slow resume

Ionic2 app resumes very slowly, white screen stays for like 20-30 seconds.

Steps to reproduce:

  1. Download
  2. Run ionic build android --prod --release.
  3. Open app and press hardware back button, app goes to background.
  4. Open app again from task manager list.
  5. Wait for 30 seconds and app is ready to use.

Any advice how to decrease resume time?