Source: Wal-Mart.

It's lonely at the top, and investors in big-box retail behemoth Wal-Mart (NYSE:WMT) have struggled with the question of how to find new growth opportunities when the company is already such a massive presence in the American shopping world. Last month, though, shareholders finally saw some signs that Wal-Mart could stand up to e-commerce rival (NASDAQ:AMZN), and hold its own in the brick-and-mortar retail world.

The question, though, is whether Wal-Mart's recent climb to new all-time record highs is sustainable, or whether the company will keep having trouble producing the revenue and profit growth investors want to see. Let's take a closer look at what went right for Wal-Mart in November, and whether there's more upside left for the retail giant.

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WMT data by YCharts.

What sent Wal-Mart stock soaring
A big part of the advance for Wal-Mart's shares came after its fiscal third-quarter earnings report, in which the retailer finally managed to report a modest 0.5% rise in comparable-store sales. Overall, revenue climbed 2.9%, and a reduction in share count was enough to offset a slight decline in net income to produce earnings per share that were $0.01 better than last year's third quarter.

Wal-Mart has looked to tap into favorable trends in a number of different areas of its business. In the grocery section, Wal-Mart has stepped up to boost its organic food offerings, seeking to eat into Whole Foods Market's (NASDAQ:WFM) long-term success by using its supply relationships and negotiating power to offer in-demand items at lower prices. CEO Doug McMillon also highlighted the performance of the company's Neighborhood Market format, with its smaller stores generating same-store sales growth of 5.5% and helping to contribute to overall revenue gains.

Neighborhood Market store concept. Source: Wal-Mart.

At the same time, Wal-Mart has done a good job of striking back at Amazon in the online retail space. On Thanksgiving Day, Wal-Mart posted its second-highest day of online sales in its history and, earlier this week, the company said that it had seen the most traffic and online orders ever in the five-day period between Thanksgiving and Cyber Monday. Users have embraced Wal-Mart's move toward mobile technology, with 70% of Wal-Mart's web traffic coming via mobile devices.

Why Wal-Mart can't declare victory just yet
Despite the big climb in Wal-Mart shares, the company is entering a key period. As the holiday season continues, Wal-Mart will need to demonstrate that it can keep fending off Amazon on the e-commerce front, as well as its big-box competitors on the brick-and-mortar front. Early results are encouraging, but with a late Thanksgiving, the holiday shopping season will be shorter this year, and Wal-Mart will have to work hard to keep shoppers interested throughout the month of December. Without a convincing rebound in same-store sales growth, it will be tough for investors to stay highly optimistic about Wal-Mart's ability to accelerate revenue gains in the future.

Source: Wal-Mart.

Moreover, Wal-Mart faces several huge long-term challenges. On one hand, the company already has a reputation for being a huge influence on local economies, with many of those sensitive to economic development initiatives criticizing Wal-Mart for its impact on smaller businesses. Even internationally, Wal-Mart hasn't been able to generate the growth that investors had hoped to see, and with store closures from Japan and China to Brazil, Wal-Mart hasn't capitalized on the global opportunities that other companies have seized with greater success. Domestically, Wal-Mart's efforts to break into the banking and finance business have met with mixed results, and it's uncertain whether its latest GoBank checking account product will fare any better than some of its previous initiatives on the financial services front.

Perhaps most discouragingly, investors still can't expect an immediate turnaround in Wal-Mart's earnings. In its November report, Wal-Mart narrowed its guidance toward the lower-end of its previous range, with expectations for between $4.92 and $5.02 in earnings per share marking a slight decline from the $5.11 per share in underlying earnings per share that Wal-Mart posted last year. Even though expectations for Wal-Mart are incredibly low right now, investors aren't likely to keep rewarding the company with higher share prices unless the retailer can prove that growth in comps is sustainable and can accelerate over time.

As nice as it is to see Wal-Mart shares climb so high in November, the real question for the retailer is whether it can break its sales slump, which has lasted for years, and start producing more sustainable gains in revenue over the long run. Without showing that it can follow through on its encouraging progress, Wal-Mart's share-price gains could be short-lived.