Owning growth stocks is a great way to potentially boost your portfolio's gains, but knowing how to select the right companies that are poised to be long-term winners isn't always easy. 

And even when you find a few great companies, you'll have to stomach some potential volatility as they build market share and invest in new areas of growth.

To help you out with this process, I'm highlighting two growth stocks below -- Upstart Holdings (UPST 2.76%) and Doximity (DOCS 0.97%) -- that are not only well-positioned to grow in the short term, but that could also be fantastic stocks to hold over the next 10 years. 

A person sitting at a desk.

Image source: Getty Images.

1. Upstart Holdings

If you've never heard of Upstart Holdings, the first thing you'll want to know is that this fast-growing tech company is a bet on the artificial intelligence (AI) loan-origination market. Upstart's platform helps pair people with lenders using AI -- and it's tapping into two massive markets. 

The company has already been successful in the $84 billion personal loan market, and it recently expanded into the massive auto loan market as well, which management projects is worth $635 billion.  

To give you an idea of just how helpful Upstart's platform has been to its 1.7 million customers, consider these stats:

  • Upstart's platform makes it easier for people to secure loans compared to traditional lending systems and also has 75% fewer loan defaults than the same approval rates of major banks.  
  • The company's personal loan rates are an average of 10% lower than traditional lenders.
  • 67% of loans originated on its platform are fully automated.

Investors should also know that Upstart gets 92% of its sales from the fees that it charges banks and lending institutions, which means that the company's revenue comes from very stable sources. 

And when it comes to growth, Upstart has it in spades. The company's sales skyrocketed 256% in the first nine months of 2021, compared to the year-ago period. And with Upstart just getting started in the automotive-loan-generation business, there's plenty of room for more growth from this company in the coming years. 

2. Doximity

Doximity has been called a LinkedIn for medical professionals, which is certainly a compliment, but the company is so much more than just a social networking tool for medical professionals to manage their careers. 

It also allows them to conduct HIPAA-compliant virtual patient visits via telemedicine -- a service that is used by more than 150 hospitals across the country -- and to keep up with medical news and research.

Doximity has already become a dominant force in its respective markets since launching in 2010 and boasts 80% of all U.S. doctors as Doximity members, as well as 50% of both nurses and physician assistants.  

Aside from the company's impressive expansion in the professional medical market, Doximity is growing its revenue at a healthy clip and the company is profitable. In the first half of 2021, sales popped 86% and net income skyrocketed more than four times what it generated from the same period in 2020.  

As the company continues to grow and tap into an estimated total addressable market of $18.5 billion -- across the pharmaceutical marketing, health system marketing and staffing, and telehealth markets -- investors may want to put Doximity on their next buy list.