The year's final quarter is underway, and investors have a huge range of variables to consider. There's no shortage of potential catalysts that could add more twists and turns to 2020's already highly volatile trading, but high-quality companies capable of shaping and benefiting from influential trends will continue to deliver strong performance. 

A small number of high-performing stocks will typically account for a large portion of a portfolio's returns over the long term. Read on for a look at three promising growth stocks that could play that role and power your portfolio for decades to come.

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1. Impinj: Bringing non-electronic items into the data revolution

Small-cap semiconductor company Impinj (NASDAQ:PI) saw sales rise by 24.6% annually last fiscal year. The radio-frequency-identification (RFID) specialist's revenue growth accelerated in the first quarter of this year -- coming in at roughly 44.6% year over year. So why did sales plummet roughly 31% year over year in Q2 and spur a substantial sell-off for the stock? The core catalyst isn't something that long-term investors should fret about.

The retail industry has been the biggest market for Impinj's products, with its RFID tags and sensors paving the way for sellers to keep better track of product inventory, shift goods to meet in-store and e-commerce demand, and help prevent theft and counterfeiting. With the coronavirus resulting in widespread retail closures last quarter and ongoing shifts in store operations and consumer behavior, Impinj's business has taken a big hit. 

The good news is that the company looks cheaply valued, and there's a good chance demand will bounce back and spur big stock gains. With Impinj currently valued at roughly $650 million and trading at about five times this year's expected sales, investors should seize the opportunity to build a position in the company.

Retail adoption for RFID tag and sensor technologies was in the early stages prior to disruption from the coronavirus, and it will likely see significant expansion over the long term despite current setbacks. Impinj's technologies are at even earlier stages of adoption in fields including manufacturing, healthcare, and hospitality, and there's huge room for growth in industries outside of retail. With the stock trading off more than 50% from its lifetime high and offering tremendous growth potential, Impinj stands out as a hot buy. 

2. Cloudflare: Enabling a better internet 

Without even knowing it, most internet users probably visit webpages on a daily basis that depend on Cloudflare's (NYSE:NET) technologies. The company might not be a household name yet, but it's supplying vital services and has attractive growth prospects. 

Cloudflare's content-delivery-network (CDN) technologies move data from central cloud servers to edge servers that are closer to users, paving the way for significantly faster webpage access. The company is also a leader in protection against attacks that can take down websites or allow bad actors to impersonate users and gain access to valuable information or accounts. In short, the company helps keep websites fast, accessible, and safe. 

Strengths in content delivery and web security should lay the groundwork for the company to introduce new services tailored to the needs of an evolving internet. The web technologies specialist recently launched a service that allows users to monitor web traffic and security trends. It also announced a new web analytics platform that will allow website owners to track important data without sacrificing users' privacy. 

Cloudflare has a market capitalization of roughly $12.6 billion and trades at about 31 times this year's expected sales. The business isn't profitable yet, and that price-to-sales multiple probably looks intimidating at first glance. However, the business grew sales 48% year over year last quarter, easily surpassing both management and Wall Street's targets, and it added more total and large-size customers than ever before. The company's industry-leading services and strong gross margins (77% last quarter) point to huge earnings potential.

3. StoneCo: Riding momentum in payment-processing services

StoneCo (NASDAQ:STNE) has significantly outperformed the broader market across 2020's trading. Its share price has climbed roughly 34% year to date, and it still has plenty of room to run.

The Brazil-based fintech company has managed to post strong performance despite weak economic conditions in its home market, and the business looks primed for big growth over the next decade as Latin American economies improve and big growth for e-commerce helps spur rapid adoption for payment-processing services in these markets. 

While credit cards, debit cards, and mobile-app based payments are commonplace in the U.S. and Europe, adoption remains at an early stage in much of Latin America. As a leading provider of payment processing services, this points to a huge growth opportunity for StoneCo. 

Total payment processing volume through the company's platform climbed 27.9% year over year despite the substantial adverse impact from the coronavirus, and total revenue climbed 13.8% in the period.

But while pressures stemming from the coronavirus have created near-term challenges for the business, the situation has also likely accelerated trends that will help spur StoneCo's growth over the long term. Closures for businesses including restaurants and brick-and-mortar retail stores put a serious damper on sales growth last quarter, but online payment volume saw big growth -- expanding 80% year over year in the quarter and 94% in July.

Brazil and other Latin American markets will see dramatic growth for e-commerce over the next decade and beyond, and this momentum is going to translate to big growth for digital payment-processing services. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.