Ideas on how my local shop makes cold espresso?

My local coffee shop has the best…..freaking best coffee I’ve ever had. It’s the most addicted to something I’ve ever been. I usually get an iced latte with flavoring. From what I’ve seen they keep these big stainless steel containers full of espresso but they’re cold for the cold drinks. I read on a thread if you do that it’s bad because espresso loses its flavor but let me tell you there’s absolutely no flavor lost. It’s a completely different taste but it’s smooth and flavorful. I can actually taste the notes. Their hot espresso is amazing too but nothing like the cold drinks. What technique could they be using? The only thing I can see it being online is heavily steeping for a strong cold brew?