We are given a text file called logs.txt, it is 953 lines long and 243 Kilobytes big:

$ wc -l logs.txt
953 logs.txt

$ ls -lh logs.txt
-rw-r--r-- 1 osiriz osiriz 243K Mar 20 10:30 logs.txt

We can find the flag with grep:

$ grep "DDC{" logs.txt
130.225.166.251 - - [25/Feb/2023:12:42:51 +0100] "POST /submit/flags/what-is-logging/DDC{CR4ZY-L0NG-F1L3S-C4N-B3-S34RCH3D} HTTP/1.1" 200 5082 "https://api.ntp-event.dk/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36 Edg/110.0.1587.50"

We can see that the flag was found as DDC{CR4ZY-L0NG-F1L3S-C4N-B3-S34RCH3D}