Boost. What does "Minimum Cache Lifetime" mean?
Check out this handbook page describing all settings (for 6.x but still relevant to 7.x):

"On high-traffic sites, it may be necessary to enforce a minimum cache lifetime. The minimum cache lifetime is the minimum amount of time that will elapse before the cache is emptied and recreated, and is applied to both page and block caches. A larger minimum cache lifetime offers better performance, but users will not see new content for a longer period of time."