The 26-year-old has won praise from Arsène Wenger in recent weeks and he believes he is playing like never before.
"I feel I'm in the best form of my life," Koscielny told arsenal.com. "I've improved a lot. I keep working on the basics, my controls and my passes.
"I'm also more rigorous. I make less fouls and get less booked as I needed time to adapt to England. I also cope better with the pressure of playing in a very big club. And I know I can improve even more.
"Chelsea was one of the best performances of my career, along with the win against Barcelona at home last season," he added. "Most importantly it's a win that will bring the team together even more and will bring great confidence."