Control circuit power supply with ATTiny45

Hey there!

I want to control a whole circuit power supply with an ATTiny45.

To be precice: I want to power down a whole ESP8266 cicuit including sensors etc. (ESP-01, BME280, LF33CV) with a sleeping ATTiny45 to save battery. Every 15min the ATTiny should power the circuit for 15Sec so that the ESP can send its measurements and then the ATTiny cuts of the power again.

My questions:

  1. Is this even possible?
  2. What kind of sleeping library I can use for the ATTiny?
  3. What kind of transistor would be suitable to power / power down the whole circuit (I think it should be able to handle max. 300mA?)? Maybe the BC639? Datasheet

Thanks in advance for your input!

No ideas? Or not possible? :confused:

1 - Yes 2 - not familiar with. 3 - I'd rather use a MOSFET and as if I remember it correctly ESP may have up to 0.5A peak consumption.