Amazon's surprisingly strong earnings report sent its stock zooming Friday, but Piper Jaffray analyst Gene Munster warned that investors shouldn't be complacent.
"Feels like the margins over the next quarters will continue to move higher, but to say we can rest easy for the next few years on that, I would say is a fool's bet," Munster said on CNBC's "Squawk Box." "You never can rest easy on Amazon because … they make such big bets."
Munster added that, during the company conference call, Amazon CFO Thomas Szkutak said e-commerce giant would continue to focus on greater productivity, "which basically means this hope for greater margins continues to be a focus."
In late-morning Friday trading, its share price was up more than 15 percent. (Click here to track the price.)
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On Thursday, Amazon delivered second-quarter results that easily beat Wall Street's expectations. Earnings per share came in at 19 cent a share on revenue of $23.18 billion.
Analysts expected Amazon to report a quarterly loss of 14 cents a share on $22.39 billion in revenue, according to consensus estimates from Thomson Reuters.
Munster said Amazon is taking the right steps in order to do away with the one weapon traditional retailers have had against it: instant gratification.
"What they've done is ramp up the number of cities with same-day delivery. It's gone up from six to 13. I think that's going to be around 50 cities in the next few years," he said. "Everybody thinks of Amazon as two-day [delivery], that's going to morph into one-day delivery."