The stock market has challenged the fortitude of even the most seasoned investors over the past year, with extreme volatility driving shares of some of the largest and most popular companies down. However, not only have there been notable exceptions to these trends, but wonderful businesses with a strong competitive edge have continued to grow in this difficult environment. 

Regardless of what stocks do in the coming weeks or months, superior businesses primed for growth can come out on top in the long run. Here are two such stocks to consider adding to your portfolio now. 

1. Vertex Pharmaceuticals 

Vertex Pharmaceuticals (VRTX 1.25%) has actually beaten the market over the trailing 12 months, delivering a share price increase of around 30% compared to the S&P 500's negative return that currently sits right around 7%. 

The company has continued its rapid growth trajectory against a backdrop of volatile market and economic conditions due to the resilience of its underlying business and the demand its products consistently generate. 

Vertex's portfolio consists of four products, all of which treat cystic fibrosis. While the market opportunity for its treatments is large -- estimates show that there are roughly 105,000 people known to have the genetic disease worldwide -- Vertex is the only drugmaker to date that has snagged approvals for CFTR modulators, which are designed to help correct the underlying protein issue that causes cystic fibrosis in the first place.  

All four of Vertex Pharmaceuticals' products are CFTR modulators. And because of the role these drugs play in helping patients combat the disease, patients are often enjoying a better quality of life and living longer. So there is a consistent need for Vertex's products, and the fact that its medicines are improving the quality and quantity of life for patients helps to promote and expand demand for them. 

Over the trailing decade, Vertex has grown its annual revenue by roughly 640%. And its profits have risen by about 60% in the past five years alone.

The company is building on the success of its profitable business to propel itself into other lucrative markets primed to disrupt their markets and provide durable revenue and earnings. This includes exa-cel, a drug it developed in partnership with CRISPR Therapeutics and for which it is currently seeking approval as a potential one-time functional cure for two rare blood disorders.

Then there is VX-522, which Vertex is developing with Moderna for cystic fibrosis patients who need a therapeutic to target the underlying cause of their disease but are unable to benefit from CFTR modulators.  The patient population is one which Vertex's management estimates could be as many as 5,000 individuals, not counting the 20,000 cystic fibrosis patients that can take CFTR modulators but are not yet doing so.  

The runway of growth for this business appears to truly be in the early stages. Given that fact, and the continued profitability of this healthcare stock, investors may be looking at a bargain price for Vertex Pharmaceuticals in light of its robust long-term potential. 

2. Airbnb 

Airbnb (ABNB 2.77%) is trading up by roughly 60% from the start of 2023, although the stock is still down by more than 20% from one year ago. While share price alone doesn't tell you much about a business, other than how the market values it at a given point in time, this stock's wild run since the start of the year has been more than warranted. 

Airbnb has continued to prove to investors -- not just in a succession of fantastic quarterly reports, but in its recently released 2022 financial results -- that its business is on a supercharged growth trajectory fueled by a diverse range of factors from the broader recovery of travel to the changing habits of travelers as a whole. 

Last year saw the company report nights and experiences booked on its platform to the tune of 394 million. Not only did this figure represent an increase of 31% when compared to the full-year 2021, but nights and experiences booked were up 20% compared to pre-pandemic levels in 2019. So, this growth isn't just from revenge travel, so to speak.  

Meanwhile, revenue growth on a year-over-year and three-year clip was incredible, and Airbnb reported its first full year as a profitable company. Its 2022 revenue came in at $8.4 billion, up 40% and 75% on a one-year and three-year clip, respectively. Last year, the company raked in total net income of $1.9 billion, along with adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) of $2.9 billion.  

Even as a recovery in short-term travel patterns continues to drive superior growth for Airbnb's business, the prevalence of long-term stays as a key growth driver also remains. Case in point: As of the final quarter of the year, 21% of all gross stays booked on the platform were long-term stays, a trip category that refers to bookings of 28 days or longer.  

Not only has its cohort of long-term stays remained stable over the past several quarters, but this segment is seeing growth that is considerably elevated from pre-pandemic levels. As CFO Dave Stephenson noted in the recent earnings call, while one-fifth of all bookings are now long-term stays, as of the first quarter of 2019 before the pandemic, long-term stays only accounted for 13% of Airbnb's total gross bookings.  

There are a wide range of possible explanations for the continued growth of this category, even as people are going on shorter trips for business and leisure again. Management has noted that the increased flexibility that travelers have now compared to before the pandemic, spurred by factors like remote work adoption, has played in integral role here. 

From vacationers to those adopting the work-and-travel lifestyle, Airbnb's platform is evolving to meet the demands of the competitive environment in which it operates while tapping into sources of growth that include both traditional and nontraditional travel. The versatility of this business, and its continued growth amid a challenging landscape, have proven the resilience of its model. Now could be an opportune time to snap up shares.