(NASDAQ:AMZN) continued to impress investors when it reported its April 27 first-quarter earnings. The report highlighted rapid growth, improving cash flow, and aggressive spending on growth opportunities, sending shares to new highs.

Here's a close look at the metrics behind Amazon's excellent performance recently.

Amazon employee with box

Image source: Amazon.

23%: Amazon's net sales in its first quarter continued to rise quickly. First-quarter revenue hit $35.7 billion, up 23% year over year. This increase was driven primarily by Amazon's 24% increase in its North America e-commerce sales, but also benefited from revenue growth internationally and in its cloud services.

43%: Amazon Web Services (AWS), or Amazon's cloud business, continues to be the company's fastest-growing segment. Though the segment's $3.7 billion in revenue during the quarter was small compared to Amazon's e-commerce revenue of $32 billion, the segment is growing to represent a larger portion of Amazon's total revenue. In the first quarter, AWS represented 10.3% of Amazon's revenue, up from 8.8% in the year-ago quarter.

89%: While AWS accounts for a minority of Amazon's revenue, the segment actually makes up the bulk of Amazon's operating income. AWS operating income accounted for 89% of Amazon's total operating income in the first quarter, up from 56% of operating income in the year-ago quarter.

53%: Given major fluctuations in Amazon's aggressive spending on growth opportunities, management understandably likes to track its operating cash flow on a trailing-12-month basis. In its first quarter, Amazon said operating cash flow was up 53% in the trailing 12 months compared to the year-ago period. Operating cash flow hit $17.6 billion, up from $11.6 billion in the year-ago trailing-12-month period.

52%: Similarly, Amazon's free cash flow jumped sharply during this same trailing-12-month period. Free cash flow hit $10.2 billion, up 52% from $6.7 billion in the year-ago trailing-12-month period.

($481): But not all key metrics are headed upward at Amazon. In the company's first quarter, its international operating loss widened from $121 million in the year-ago quarter to a loss of $481 million, despite international net sales during this period increasing from $9.6 billion in the first quarter of 2016 to $11.1 billion in the first quarter of 2017.

Amazon's wider loss internationally comes as the company aggressively expands its offerings overseas, namely in India where Amazon has increased its Prime selection by 75% in the last nine months and where it has boosted fulfillment capacity for sellers by 26% in 2017 alone.

$4.7 billion: Highlighting Amazon's relentless investments in its ability to fulfill orders, the company incurred $4.7 billion in operating expenses related to fulfillment in the first quarter of 2017. This is up 27% compared to Amazon's $3.7 billion in fulfillment operating expenses in the year-ago quarter.

Amazon boxes in Amazon fulfillment center

Image source: Amazon.

$34.7 billion: Amazon's total operating expenses in its first quarter climbed from $28.1 billion in 2016 to $34.7 billion in 2017. The outsized year-over-year increase in operating expenses meant Amazon's operating income in its first quarter declined slightly. First-quarter operating income was $1.01 billion, down from $1.07 billion in the year-ago quarter.

For its first quarter, Amazon investors seemed to easily forgive the company's year-over-year pullback in operating income as Amazon ramped up its expenses. Solid revenue growth, surging trailing-12-month operating cash flow, and big success in the cloud stood out enough to keep investors excited about Amazon's long-term potential.

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