2018 was tough for Facebook (NASDAQ:FB). Though the social network's stock hit an all-time high of $218.62 last summer, it finished the year 26% lower than it started as investors worried about the company's decelerating growth and rising operating costs amid its efforts to improve security and privacy on its platform.

But sentiment toward Facebook has improved significantly this year, with shares up a whopping 36% year to date. This strong rebound, of course, puts immense pressure on the company's first-quarter update. Investors will be looking for Facebook to show that its strong growth story is still intact.

Here's an overview of some specific areas to watch when Facebook reports results later this month.

Facebook CEO Mark Zuckerberg speaking onstage at F8 2018

Facebook CEO Mark Zuckerberg at F8 2018. Image source: Facebook.

Revenue growth

Though Facebook's revenue growth has been decelerating recently, growing 30% year over year in Q4 compared to 49% growth in the first quarter of 2019, the pace of deceleration moderated in Q4. In Q2 and Q3 of last year, for instance, Facebook's year-over-year revenue growth rates were 42% and 33%, respectively. These growth rates represented a significant slowdown compared to 49% year-over-year growth in Q1. Fourth-quarter year-over-year revenue growth of 30%, therefore, may have been slower but it highlighted resilience in the company's strong top-line growth.

To this end, Facebook's fourth-quarter revenue of $16.9 billion came in at the high end of management's guidance and beat analysts' expectations. Management had guided for fourth-quarter revenue to rise 24% to 30%.

For Facebook's first quarter, management said it expected revenue to rise 24% to 26% year over year. Given the market's growing optimism for the stock recently, investors should look for revenue growth for the period to be close to the high end of this range.

Operating costs

Facebook's operating expenses jumped sharply in 2018, rising 51% year over year. Expenses climbed particularly rapidly toward the end of the year, soaring 62% in Q4 to $9.1 billion.

"In addition to continued investment in infrastructure, safety and security, and innovation, expenses were also driven by seasonal factors -- including marketing efforts," explained CFO David Wehner in the company's fourth-quarter earnings call.

Further investment in investment in infrastructure, safety, and security are expected to result in more sharp expense growth in 2019, with management guiding for expenses to rise 40% to 50% compared to 2018. Investors, therefore, should look for operating expenses to rise at a rate within this range.

Users

Finally, investors should check on Facebook's user growth, particularly the company's measure of monthly active users across its entire family of social networks, which includes Facebook, Instagram, Messenger, and WhatsApp. Facebook said 2.7 billion people used at least one of its apps in December, with more than 2 billion active daily. Approximately 2.5 billion and 2.6 billion users interacted with at least one of these apps in Q2 and Q3, respectively. Can this metric hit 2.8 billion in Q1?

Facebook is scheduled to report its first-quarter results on Wednesday, April 24, after the market closes.