Costco (COST 1.03%) has some high expectations to try to meet in just a few days. The warehouse retailer's stock has trounced the market in the weeks leading up to Thursday's earnings report, which sets up a potentially volatile trading week ahead.

The chain erased some of the mystery about that report by releasing monthly sales trend data on Dec. 1 that showed solid growth momentum at the start of the holiday shopping season. But the full earnings picture, including profitability and membership metrics, will be part of Costco's quarterly report on Dec. 9.

Let's look at the metrics worth following in Thursday's announcement.

The sales update

Costco's last monthly sales report covered the period through Nov. 21. That announcement showed solid growth, with comparable-store sales rising 9% after adjusting for gas price swings and currency exchange moves. Comps through the 28th of the month landed at 10%, roughly even with the strong expansion pace investors have seen in recent months.

Thursday's update will add context around that growth figure by revealing customer traffic and gains across categories like food and consumer electronics. Shareholders are hoping to see strength in that last category, since it might imply a solid holiday shopping quarter ahead.

Membership metrics

Investors will get some important updates on Costco's membership trends, which are critical because the company derives most of its earnings from its subscriptions. Membership fees should rise due to the combination of a growing customer base and greater penetration of its executive level product. For context, fee income rose to $3.9 billion over the previous 12 months compared to $3.5 billion a year earlier.

An employee restocks fresh vegetables.

Image source: Getty Images.

We'll also learn whether Costco managed to maintain -- or even improve on -- its stellar renewal rate. A full 91% of members have been choosing to renew their subscriptions in recent months, representing a record high for the business.

A steady boost there would be the surest sign yet that shoppers are getting plenty of value from their memberships. Lower renewals, on the other hand, might imply pricing challenges or encroaching competition.

Looking ahead

Costco investors have high expectations for sales this year, with revenue expected to rise to $214 billion on top of last year's soaring results. The management team won't issue a detailed outlook on that score, but executives should comment about the strength they're seeing in the industry now that the peak shopping season is underway.

The retailer stock's rally over the last few weeks suggests that there's lots of good news already incorporated into the share price. Costco is a more valuable business today than it was before the pandemic struck. It has a much larger sales base, after all, and millions of additional paying members.

Those assets should serve shareholders well over the next few years, especially as Costco looks to implement its next increase in the annual membership fee. Yet investors should balance that optimism against the likelihood of slower growth ahead following several years of above-average revenue gains.