First of all there is a security screening when entering the terminal building.
Skip the line as TK C / TK *G guest by telling your driver to drop you at the last entrance of the international terminal building. There is a separate entrance for TK C / TK *G guests.

When checked in, you have the entrance to your back. Turn left and go to the very end of the terminal building. There is a landside entrance to the lounge with a dedicated security screening and immigration counter. Only for TK C guests or Elite+ travelling on TK. That is quicker than the regular fast track counter.

The only time of day where that entrance is busy is between 06:00 and 06:15 a.m. as the landside entrance only opens at 06:00 a.m.

While rushing through the lounge at that time of day a quick espresso will surely be appreciated.

Boarding time according to the boarding passes issued in Istanbul is one hour ahead of scheduled departure time. That is a leftover of the times when the second security screening was directly at the gate.

If I have a flight boarding at gates 219-226 I leave the lounge T- 25 minutes, all other gates T - 35 minutes and even then there is still a line to board the plane.

I usually plan to be at Atatürk airport 1:15 hours before departure. TK is very efficient for those guests that just want to "fly" through the airport.