I had problems getting my large-case solutions to pass the time limit for some of the Snackdown 1A and 1B problems, despite using (I think) the intended strategy.
For example, I did CHEFKO in 1B with a priority queue but still had TLE. There were no successful Ruby submissions to look at, but the successful Python solutions revealed that a 5 sec limit was given, compared to only 3 sec for Ruby.
Why the difference? Ruby is not a quicker language AFAIK.