A stock market sell-off can be intimidating. Nobody likes logging into their brokerage account and seeing their balance well off its highs. However, anyone with an investment horizon longer than three to five years should also consider this a buying opportunity, as many stocks are trading for much cheaper than they used to.

By sifting through the stocks that have been drastically sold off, investors can pick up a few fantastic businesses for cheap. Among those that I think are bargains right now are Alphabet (GOOG 0.10%) (GOOGL -0.02%), MercadoLibre (MELI 1.65%), and Twilio (TWLO 1.74%). This trio's stock prices are well off their highs, but if you've got a long-term investing horizon, then these stocks are set to produce significant returns.

Alphabet

Alphabet's stock has been sold off for one reason: Advertisement budgets get slashed in a weak economy. With more than 80% of Alphabet's revenue coming from advertisements, investors are worried about what might happen in the near term. However, this stock is a bargain buy for its future prospects, not its immediate ones.

Amid a challenging advertising environment, its Google search division still managed to grow its revenue by 14% year over year in the second quarter. This growth demonstrates how vital it is to customers to spend on Google versus other Alphabet platforms like YouTube (its revenue only grew 5% year over year). Still, even with the company's overall 13% growth rate, Alphabet's operating margin dropped from 31% last year to 28%.

These results reflect a problematic advertising quarter, and the rest of the year may hold the same disappointing results. However, once the economy recovers, advertising spending will come roaring back, causing Alphabet's revenue and profits to rise rapidly. This sentiment shift will occur quickly, so investors need to consider purchasing Alphabet's stock now.

At 22 times earnings, Alphabet's stock isn't cheap, but this price-to-earnings ratio reflects a lower-margin quarter, thus impacting its earnings. I think Alphabet is a great buy here; you just have to be patient with the stock and hold on until the economy is booming again.

MercadoLibre

In Latin America, MercadoLibre is the king of e-commerce. With its online marketplace, digital payment system, consumer credit division, and shipping logistics solution, MercadoLibre has a lot of irons in the fire.

This diversification is crucial because it insulates the company from having a weak quarter companywide versus a weak quarter isolated to a business division. For example, in Q2 this year, MercadoLibre grew its revenue 57% year over year to $2.6 billion. However, its two divisions had entirely different quarters.

Division Revenue Growth (YOY)
Commerce $1.4 billion 23%
Fintech $1.2 billion 107%

Data source: MercadoLibre. YOY = year over year. 

While 23% growth in commerce is nothing to sneeze at, 107% growth in the fintech segment completely overshadows commerce's weaker quarter.

Despite this impressive quarter, MercadoLibre still trades like a beaten-down e-commerce stock. Compared to other e-commerce companies like Etsy and Shopify, MercadoLibre is lowly valued.

MELI PS Ratio Chart

MELI PS Ratio data by YCharts

A lot goes into valuation, but MercadoLibre being priced well below its peers seems odd, as it is executing much better than either of those businesses. Furthermore, MercadoLibre has been trading well below its average price-to-sales ratio over the past decade.

E-commerce growth may be slowing in the U.S. temporarily, but it's just in its infancy in Latin America. This growth runway makes MercadoLibre an outstanding stock to buy on the dip.

Twilio

If you've ever received a text message from a business to confirm an appointment or communicated with an Airbnb host through text messages, then you've interacted with Twilio's product. It's not easy to write the code necessary to facilitate this communication, so many businesses (especially smaller ones) couldn't do it without the help of expensive software engineers. However, Twilio's application program interfaces (APIs) provide a solution that requires no coding.

As businesses pay for each message they send, it makes sense that Twilio's revenue is rising. Twilio's Q2 organic revenue rose 33% year over year, so it's clear businesses are still finding value with this communication medium. Co-founder and CEO Jeff Lawson said in a statement he sees this trend continuing as he reaffirmed his 30% organic revenue growth projection through 2024. Furthermore, he highlighted an eight-figure deal (at least $10 million) signed by a Fortune 100 retailer that wanted to "reimagine their customer experience."

The drive for businesses to better communicate with their customers has been going on for centuries, and Twilio is at the forefront of the next iteration of customer communication. With the stock trading at its all-time low valuation of 4.9 times sales and down 80% from its all-time high, there's a lot of upside to Twilio's stock.

All three stocks are dealing with short-term negative market sentiment, but the businesses are all in great shape for the long term. Investors need to be business-focused and not sentiment-focused, as business results drive stock returns over the long term. With all three businesses still executing well, they make great buys in today's market.