This is the original email by the person who discovered this backdoor. But if you want you can search for xz backdoor and you'll find a lot more articles which explain timelines and other things. https://www.openwall.com/lists/oss-security/2024/03/29/4

 == Observing Impact on openssh server ==

With the backdoored liblzma installed, logins via ssh become a lot slower.

time ssh nonexistant@...alhost

before:
nonexistant@...alhost: Permission denied (publickey).

before:
real	0m0.299s
user	0m0.202s
sys	0m0.006s

after:
nonexistant@...alhost: Permission denied (publickey).

real	0m0.807s
user	0m0.202s
sys	0m0.006s

That's a 500ms or 0.5s difference