For all the nail-biting about the economy over the past year, investors had it easy: a 5% yield on short-term U.S. debt, one of the safest investments in the world. Now, the times they are a-changin’—again.

U.S. stock index futures edged lower on Friday, taking a pause from the previous session's rally that set Wall Street's main indexes on track for weekly gains after the Federal Reserve took a pivotal stance on monetary policy earlier in the week.

Asian stocks have surged, with Japan’s Nikkei 225 index leading gains after Wall Street romped to records following the Federal Reserve’s big cut to interest rates.