Today when I was looking at my in contest submissions, I noticed that my D submission passed system tests in 639 ms. However, I remembered that it passed pretests in 872 ms 96579469. I checked my terminal history (I use cf tool for submitting) and it turns out my memory was correct.
Now, 200 ms difference and AC vs TLE is quite large. Is there a reason behind this, and could this be related to the queue at the beginning of the contest?