As the calendar flips to 2023, a few stocks are reaching screaming-buy territory. While I'm a long-term investor, I still pay attention to short-term movements to pounce on fantastic buying opportunities. I can increase my long-term return percentage by grabbing stocks on sale.

Two stocks that can help me accomplish this are Alphabet (GOOG 0.77%) and CrowdStrike (CRWD 0.71%). Both have reached a relative valuation low due to each business experiencing headwinds. However, the long-term trajectory of both companies is still positive, which gives me confidence in the investments.

1. Alphabet

Alphabet is primarily an advertisement play. With its Google, YouTube, and Android properties, nearly 80% of revenue comes from ads on its platforms. However, advertising hasn't been a great area to be in recently.

First, economic conditions severely affected the advertising market. As advertising budgets are slashed to save on expenses, there is less demand for ad space. In response, ad prices fell, which hurt Alphabet's revenue.

This is only a temporary headwind, as many businesses are doing this in preparation for a potential downturn. If this doesn't happen, the pent-up demand will return in force and boost Alphabet's revenue. However, another force is also at play.

Alphabet might be losing market share to competitors. According to Insider Intelligence, Meta Platforms (parent company of Facebook and Instagram) and Alphabet recently lost the combined control of the advertising market They're now commanding a 48.4% combined market share. This loss is due to increased competition from other tech giants like Amazon, Microsoft, and Apple, as well as newcomer TikTok. Still, digital advertising is a growing industry, so Alphabet can lose market share and grow revenue.

With how often Google, Androids, and YouTube are used daily, I don't see these platforms going anywhere, so Alphabet's temporary revenue growth slowdown shouldn't last forever.

I think now is a timely opportunity to purchase the stock, due to its free cash flow yield. Essentially, this is how much free cash flow is generated per share (similar to a dividend yield). Currently, it's the highest it has been in nearly a decade.

Chart showing rise in Alphabet's free cash flow yield since 2020.

GOOG Free Cash Flow Yield data by YCharts

With Alphabet kicking out a massive amount of cash flow per share, the stock appears undervalued -- especially since it's yielding higher than a 10-year Treasury. While concerns about rising expenses are valid, the management team is taking steps to control expenses.

Alphabet's current situation is not as dire as the valuation and stock price movement seem, so the stock makes for a top buy.

2. CrowdStrike

An area that won't experience a spending slowdown is cybersecurity. With threats increasing daily and most companies behind the clock in providing adequate security, this sector is highly intriguing for many investors. One of the top companies in this space is CrowdStrike, which provides endpoint protection (on phones and laptops) and cloud workload security.

With 23 products and counting, CrowdStrike has multiple options that its customers can add to expand their cybersecurity offering. In fact, 60% of its customers use five modules or more, and 21% employ seven or more. That leaves much room for expansion, and customers have done just that.

CrowdStrike's retention rate was 124% in the third quarter of FY 2023 (ending Oct. 31), meaning existing customers spent $124 for every $100 they spent last year. That is up from the first quarter's 120% and the second quarter's 122%, showing clients aren't afraid to increase their spending in the face of a potential economic downturn.

Like Alphabet, CrowdStrike's free cash flow yield is up to 2.5%, the highest it has posted as a public company. While it's not cheaper than the 10-year Treasury yield, it's an impressively high yield for a company growing its annual recurring revenue by 54% year over year to $2.34 billion as of Q3.

There are some concerns about slower customer acquisitions heading into next year, but that should ramp up again when the economic uncertainty is resolved. Until then, existing customers will drive much of CrowdStrike's growth. Still, CrowdStrike grew its customer count by 44% to 21,146 in Q3, so slower customer growth (say even 30%) is still quite impressive.

CrowdStrike's offerings are top-notch (G2 named it a leader across 16 categories), and it is riding the wave of cybersecurity adoption across the enterprise. As a result, it's a top-tier stock to own for the long haul, and investors should use the stock's weakness to establish a position.