Checking the cause of a high TTFB (Time To First Byte) can be time consuming. And pinpointing the issue requires multiple tests against even the smallest changes. Enter Apache’s Benchmarking Tool ab to help with quick testing.
ab -n 100 http://www.website.com/
The above command will execute 100 tests against the website entered. The results are displayed based on averages from the test. For TTFB, just review the Processing line in the results.
ab comes standard with Apache server installs, and is included in OSX.
For more details on settings and parameters for the ab, checkout the apache manual page: https://httpd.apache.org/docs/2.4/programs/ab.html.