Just when Shopify (NYSE:SHOP) starts to look like it can't go any higher, it does. At least that's how shares of the e-commerce platform company have seemed to perform recently. The stock has soared more than 120% year to date -- and that's on top of a 37% gain last year.

Investors have been impressed with Shopify's strong revenue growth and improving profitability as new merchants flock to the platform and more merchants pay for the company's Plus subscription plans. Such strong performance, of course, means expectations are high going into Shopify's Aug. 1 earnings report. 

Ahead of the important quarterly update, here's a preview of some key areas for investors to watch.

A laptop, tablet, and smartphone all displaying the Shopify e-commerce platform

Shopify e-commerce platform. Image source: Shopify.https://cdn.shopify.com/assets2/press/resources/photo-desk-56cfc3d26b55289a7b02f5e8b6f1d63b89565ff615e8ac4bf883ed19f8cb1bce.jpg

Revenue growth

Shopify's top-line growth has been impressive recently. Revenue in the company's first quarter surged 50% year over year to $320.5 million, handily beating management's guidance for first-quarter revenue of between $305 million and $320 million. The strong quarter reflected "the diversity and strength of our growth drivers and the solid execution of our strategy," said Shopify CFO Amy Shapero in the company's first-quarter earnings call.

For Shopify's second quarter, management guided for revenue to be between $345 million and $350 million. The midpoint of this guidance range represents 42% year-over-year growth. Analysts, however, expect Shopify's revenue to rise 43.1% year over year to $350.5 million. 

Shopify Plus

One key catalyst for Shopify's growth recently has been a robust uptake of its Shopify Plus subscription, or its e-commerce platform subscription for high-volume merchants. During Q2, Shopify Plus represented 26% of the company's $44.2 million in monthly recurring revenue (MRR), up from 22% of MRR in the year-ago quarter.

First-quarter momentum in Shopify Plus benefited from "a strong sales team that is constantly improving as well as a strong mix of upgrades," said Shopify Chief Operating Officer Harley Finkelstein in the company's first-quarter earnings call.

Investors should look for more strong performance from Shopify Plus in Q2.

Shopify Payments

Helping drive the company's gross merchandise volume (GMV) during the quarter was a 65% year-over-year increase in the e-commerce specialist's native payments processing technology, Shopify Payments. The outsized growth of Shopify Payments GMV versus the company's 50% increase for total GMV meant that Shopify Payments grew to represent 41% of total GMV -- up from 38% of GMV in the year-ago quarter.

While Shopify is unlikely to sustain such sharp growth in Shopify Payments GMV over the long haul, investors should at least look for the metric to continue outpacing total GMV growth.

Shopify reports its second-quarter results before the market open on Thursday, Aug. 1.