It would be great if stock market activity was evenly distributed throughout the day but the actual profile has huge spikes. Here in the US, normal market hours are 9:30-16:00 Eastern and much of the activity on a typical day is at market open as well shortly before market close. Also, news events can cause spikes at any time throughout the day.

This sort of transaction profile is a real challenge in capacity planning because one must plan for the peaks rather than the average and every millisecond counts due to the time-sensitive nature of these transactions.