Analysts are almost universally optimistic about Amazon.com Inc., one of the biggest winners this earnings season. But further near-term gains may be harder to come by.

Fueled by resurgent profit and revenue growth, shares of the e-commerce and cloud-computing company have risen 5% this month while Apple Inc., Microsoft Corp., Alphabet Inc. and Nvidia Corp. have all fallen. But, after adding nearly $600 billion in market value this year and with earnings out of the way, some say a fresh spark is needed amid signs of a stalling big tech rally.