For Pixel, we recommend you do the following two things:
Turn off Battery optimization* for Bob:
Go to Settings → Apps & notifications → Advanced → Special app access → Battery optimization
Scroll to Bob and select it → select “Don't optimize”
Turn off Adaptive battery for Bob:
Go to Settings → Battery → Adaptive Battery
Scroll to Bob and turn off Adaptive Battery
*Despite the term “Battery optimization”, switching to this state should not change the usage in a significant way. Bob is already optimized to use a very low battery power. In fact, this is actually the guideline of both Android and iOS – not to explicitly close apps (excluding cases such as radio or navigation apps).