Amazon (NASDAQ:AMZN) did it again. The company exceeded its own guidance and crushed analyst estimates. Its first-quarter performance was astounding, featuring 43% year-over-year revenue growth, $1.9 billion of operating income, and triple-digit growth in earnings per share.

But a look beyond key metrics reveals even more reason to keep betting on this fast-growing e-commerce juggernaut. During Amazon's earnings call, Amazon's CFO shed light on three areas investors could easily overlook: the company's advertising business, a 20% price increase to Amazon Prime, and strength in Amazon's biggest segment.

A box sitting on someone's doorstep

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Advertising: Now a "multi-billion program"

Amazon's fastest-growing segment in its first quarter wasn't online stores or subscription services. It wasn't even its cloud-computing business, or Amazon Web Services (AWS). It was Amazon's "other" segment. The segment saw revenue rise 139% year over year, or 132% year over year in constant currency. Furthermore, even after adjusting to exclude an incremental $560 million that was included in Amazon's first quarter as a result to a change in the company's revenue recognition policies during the period, year-over-year growth in the segment was still 73% -- higher growth than any other segment. This is up from 53%, 58%, and 60% year-over-year growth rates in the second, third, and fourth quarters of 2017.

Amazon's fast-growing advertising business is driving this growth, as Amazon CFO Brian Olsavsky explained:

I would say advertising continues to be a bright spot, both from a product standpoint and also financially. It continued to be a strong contributor to profitability in Q1. It's now a multi-billion-dollar program. You can see in our supplemental revenue disclosure it's in "other revenue," and it's the majority of the other revenue in that line item.

Total other revenue in Amazon's first quarter was $2.03 billion, up from $850 million in the year-ago quarter.

About Amazon Prime's price increase

One surprise announcement during Amazon's earnings call was that the company planned to increase the price of its Prime membership in the U.S. from $99 to $119 annually for new members as of May 11. In addition, the price increase will go into effect for membership renewals beginning June 16. This marks Prime's second price increase, with the first occurring in March 2014.

Olsavsky explained the main reasons for the price increase during the company's earnings call:

We continue to increase the value of Prime, including speed, selection, and digital entertainment options. We've been expanding free, same-day shipping and one-day options. In our two-day shipping, it's now available on over 100 million items, up from 20 million as recently as 2014. We continue to add digital benefits like Prime Video. The value of Prime to customers has never been greater.

The cost is also high. As we pointed out, especially with shipping options and digital benefits, we continue to see a rise in cost.

Earlier this month, Amazon said in its annual shareholder letter that its Prime members recently exceeded 100 million paid subscribers globally. 

Amazon's accelerating growth in North America

Though Amazon breaks out its revenue into online stores, physical stores, third-party seller services, subscription services, AWS, and other in its supplemental financial information portion of its financial statements, the company also divides total revenue into three major segments: North America, international, and AWS.

With about 60% of Amazon's revenue coming from North America, the segment is considered to be more mature than Amazon's international and AWS segments. This is why it's good to continue to see more strong growth in the segment. Amazon's revenue in its North America segment increased 46% year over year in Q1, up from 24% growth in the year-ago quarter. Even when excluding revenue from Amazon's recent acquisition of Whole Foods, the segment's revenue increased about 25% year over year.

Amazon CFO Brian Olsavsky credited the segment's continued strong growth to several different factors:

The general driver continues to be Prime and Prime Flywheel. We see strong customer demand, not only for the benefits that we associate with Prime. We're seeing better engagement with Prime benefits, especially digital benefits. That is always good news for eventual sales of other things. We're also selling more subscriptions -- Music Unlimited, Kindle Unlimited -- there's a number of services. There's different revenue streams that we see.

With the growth drivers for North American revenue seeming to be broad-based, strong revenue growth in Amazon's largest segment looks poised to persist in the coming quarters.

Overall, Amazon's earnings call reinforced the powerful momentum the e-commerce giant is seeing across its business.