This time last year, shares of e-commerce and cloud-computing company Amazon.com (NASDAQ:AMZN) could have easily looked like they had already exhausted much of their upside potential. Trading at $968 at the time, shares were up 25% in the trailing-12-month period ending Aug. 13, 2017, and they were up 83% in the two-year time frame leading up to that date. But Amazon stock has continued to surge higher, rising 97% in the last 12 months -- nearly doubling to $1,910 at the time of this writing.

With such a monstrous run-up behind it, it's a good time to reflect on what has driven the stock so much higher over the past 12 months. Catalysts for the stock include fast-growing revenue, skyrocketing earnings per share, huge growth in Amazon Web Services, and more.

Here's what investors should know.

Boxes in an Amazon fulfillment center

Image source: Amazon.com.

1. Sales are up 39%

During the past 12 months, strong execution across Amazon's business has led to a 39% year-over-year increase in sales. Even when excluding incremental revenue generated from Amazon's August 2017 acquisition of Whole Foods, the company's trailing-12-month revenue is up 36% year over year -- a significant acceleration from 27% year-over-year sales growth in 2016 and 31% growth in 2017. 

2. EPS skyrocketed 221%

Amazon's trailing-12-month EPS has risen 221%, fueled by strong revenue growth and a widening operating margin. Amazon's trailing-12-month operating margin has risen from 2.3% one year ago to 3.5% today. Similarly, Amazon's operating margin for its just-reported quarter was 5.6%, up sharply from 1.7% in the year-ago quarter.

3. Free cash flow increased 9%

Amazon's annualized free cash flow, or operating cash flow less capital expenditures, has risen 9% year over year to $10.4 billion. While this increase hasn't kept up with revenue growth, it's a notable boost considering Amazon's trailing-12-month capital expenditures are up 39% year over year.

4. Amazon Web Services revenue has risen 46%

Strong momentum in Amazon's cloud-computing business, Amazon Web Services (AWS), has persisted over the last 12 months. Trailing-12-month AWS revenue is up 46% year over year -- right in line with the 46% trailing-12-month growth rate Amazon boasted this time last year. Even more, AWS sales growth has picked up its pace more recently, rising 49% year over year in Amazon's most recent quarter.

5. North America sales are up 42%

Even with trailing-12-month North America sales (when excluding sales from AWS) rising to a meaty $88.5 billion this time last year, the important geographic segment has continued to grow at a robust rate. Trailing-12-month North American net sales are up 42% year over year to $125.6 billion. When excluding the impact of the Whole Foods acquisition, sales are up 26%. This is an acceleration from the 24% year-over-year growth Amazon saw in its core geographic segment for the trailing-12-month period ending this time last year, suggesting the segment has plenty of upside left.

These metrics show that Amazon stock's sharp rise over the last 12 months wasn't fueled by blind investor exuberance, but rather by uncanny growth in Amazon's underlying business. Amazon's impressive execution, then, makes the stock worth holding onto -- even at these higher levels.

John Mackey, CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool's board of directors. Daniel Sparks has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Amazon. The Motley Fool has a disclosure policy.