Following market close today, Amazon (AMZN -1.43%) will report its first-quarter results. After obliterating analyst estimates in recent quarters, expectations are high for Q1.

Sure, a natural deceleration in the company's top-line growth rate is expected as the economy reopens and consumers resume more in-person shopping. But investors are still expecting some big growth from the e-commerce and cloud-computing giant. Can Amazon deliver?

Ahead of the company's update today, here's a preview of three key items investors should check on when Amazon posts its results.

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1. Revenue growth

In Amazon's fourth quarter of 2020, sales soared 44% year over year to $125.6 billion. For some more context, Amazon had never garnered over $100 billion of revenue in a single quarter before its Q4 report. But in Q4, sales were more than $25 billion greater. It was a blockbuster quarter, to say the least. 

For Amazon's first quarter, however, management guided for a slower growth rate. The company said it expects first-quarter revenue to increase 33% to 40%. Analysts, on average, expect sales to grow 38.5% year over year.

The expected deceleration makes sense. In Q4, Amazon benefited from strong demand trends from people staying at home and elevated spending on household staples and home products. Further, Q4 included Prime Day -- a shopping event that usually falls in Q3.

2. Amazon Web Services

Though the bulk of Amazon's sales come from its e-commerce business, more than half of its operating profits are sourced from its cloud-computing business -- Amazon Web Services (AWS). The fast-growing and lucrative segment remains a key catalyst for the company this year.

In Q4, AWS revenue increased 28% year over year. Investors should look for similarly strong growth from the important segment in Q1.

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3. Guidance

Though Amazon's first-quarter results are important, the most telling metric from the update may be management's revenue outlook for Q2. There's a lot of uncertainty about how well Amazon's growth rate will fare when it's up against tough comparisons from during the pandemic, when e-commerce sales surged.

Consider that in Amazon's second quarter of 2020, net sales soared 40% year over year -- a huge acceleration from the 26% growth Amazon saw in the first quarter of 2020. Analysts are unsurprisingly anticipating a significant slowdown in Q2. On average, they expect Amazon's second-quarter revenue to increase 22% year over year. 

Amazon will report its first-quarter results after market close today -- likely sometime shortly after 4:00 p.m. EDT.