With this trick you’ll be able to instantly open the app on mobile instead of waiting for the usual 10-ish seconds. It worked with my phone which is 6 years old! And yes, I tried locking the app in the background and disabling the power saver but it still got killed in the background. 
Basically we’re gonna use an app that will automatically open Logseq every X minutes in the background.
As a nice bonus for those who use Logseq Sync, the app will sync in the background so this bottleneck is also eliminated when you open the app. (Disclaimer: I could only test it on Android. I don’t think it’s possible on iOs)
- Install Macrodroid.
- Open it.
- Tap the + button.
- Tap the “+” next to Triggers.
- Tap “Date/Time”
- Tap “Regular interval”
- Select 1 minute and tap ok
- Click on the “+” next to Actions
- Tap “Applications”
- Tap “Launch application” and OK
- Choose Logseq and then OK
- Click on the “+” next to Actions again
- Choose “Device actions”
- Choose “Launch home screen” (so that you won’t see Logseq every single time you unlock your phone)
The next steps make sure that Logseq will be opened only when the screen is off and not while we’re using other apps.
- Tap the “+” next to Constraints
- Tap “Device state”
- Tap “Device locked/unlocked”
- Tap “Device locked” and OK
- Give the macro a name
- Save the macro with the check button in the bottom right.
- Lock Macrodroid in the background and disable any battery saver for this app.