Whether you've been investing for years or just recently started building your portfolio, you're in good company if you've rejoiced at the series of new highs the S&P 500 has set to kick off 2024. As a long-term investor, you will inevitably face bull markets, bear markets, and everything in between.

The good news is, great investment opportunities don't only occur on roaring market days and great businesses make themselves known in all environments. If you're on the hunt for unstoppable growth stocks to add to your portfolio now and hold for the next several years at least, here are two no-brainer buys to add to your basket sooner than later.

1. Palantir

Palantir (PLTR 0.93%) continues to cement its leadership in the field of data analytics. The company is known for its products like Gotham, used by the U.S. intelligence community and the Department of Defense. Its Foundry product is used by government clients and large commercial enterprises. The use cases for its data analytics solutions range from counterterrorism analysis to training machine learning models to streamlining drug development processes.

A newer addition to Palantir's software solutions is its Artificial Intelligence Platform (AIP). AIP covers a wide range of possible AI solutions for Palantir's clients, including merging the power of existing software offerings of Foundry or Gotham with large language models. Through this newest product offering, Palantir is not only expanding its long-term market opportunity but diving headfirst into the explosive world of AI. Ryan Taylor, the company's chief revenue officer and chief legal officer, said the following in the company's 2023 earnings call:

In October, we set a goal of executing 500 AIP bootcamps within one year. We have already blown that goal out of the water, having completed more than 560 bootcamps across 465 organizations to date. ... We're already seeing evidence of bootcamps helping to significantly compress sales cycles and accelerate the rate of new customer acquisition, which rose to 22% sequentially for U.S. commercial in Q4 versus 12% and 4% in Q3 and Q2, respectively. And we more than doubled the number of U.S. commercial deals with TCV [total contract value] of $1 million or more from the fourth quarter in 2022 to 2023.

While Palantir used to be wholly reliant on government clients, and these still account for a large portion of revenue, its commercial clients are quickly accounting for more of its financial growth. In 2023, overall revenue totaled $2.2 billion, a 17% increase from the prior year. About half of that total, or $1 billion, was attributable to Palantir's commercial clients, up 20% from 2022.

Revenue from government clients made up the remaining $1.2 billion, which grew at a slightly slower clip but still a healthy 14%. Palantir generated profits according to generally accepted accounting principles (GAAP) of $210 million last year, while cash from operations for the full year totaled $712 million.

The company signed deals with one of the largest car rental companies, one of the largest pharmaceutical companies, and one of the largest telecommunications companies in the world last year, each over $25 million. It also signed multimillion-dollar deals with a comprehensive health network in the U.S. and one of the world's largest equipment rental companies, according to management.

The company's expanding commercial client base as a driver of overall revenue bodes particularly well for this business, and the rapid adoption of its AIP has been a notable factor here. Taylor also noted on the 2023 earnings call that the company is seeing multiple common trends related to adoption of its AIP. One is a new customer attending a bootcamp and signing an enterprise contract later. Another is a company using Palantir's solutions through a pilot program, getting introduced to its AIP, and then converting to a multiyear contract.

There's a lot of room for this company to run as it harnesses its own growth story amid the AI boom and builds upon new and existing partnerships. This most recent quarter was the fifth consecutive in which Palantir was GAAP profitable. For long-term investors, the stock is looking ripe for the picking.

2. Airbnb

Airbnb (ABNB -1.21%) built a platform designed for any type of traveler. Whether you're looking for a place to stay for a few nights, weeks, or months, chances are you can find something to suit your needs.

From full-service apartments all over the world to home stays, to unique accommodations like treehouses and one-of-a-kind curated vacation homes, Airbnb is leaning heavily into the vision of the future of travel. And at a time when the expansion of remote and flexible work is impacting virtually every industry, many workers have a level of location independence that was unheard of five to 10 years ago.

Airbnb continues to derive considerable growth from both short- and long-term stays. Its platform serves both the supply and demand sides of the travel accommodation dynamic, without carrying the costs of the actual assets since Airbnb doesn't own the properties. As of the final quarter of 2023, long-term stays of 28 days or more accounted for approximately one-fifth of gross nights booked.

People are increasingly living on Airbnb for longer periods, too. As of the end of the year, about 25% of Airbnb's long-term stay bookings were for trips of three months or more. In fact, management reported in the company's annual earnings release that nights booked for trips of more than three months rose 20% in the fourth quarter of 2023 compared to the fourth quarter of 2022.

It's not just that more people are looking to stay on Airbnb, either. People are increasingly looking to Airbnb as a way to replace or add to an existing income. Airbnb achieved a new record high in its quantity of active listings, with its active listings in the final quarter of 2023 representing an 18% increase on a year-over-year basis.

Revenue for 2023 totaled just shy of $10 billion, up 18% from 2022 and 106% from the pre-pandemic year 2019. Net income for the 12-month period totaled just under $5 billion, up 153% from 2022. Airbnb also generated free cash flow of $3.8 billion in 2023. Travelers booked 14% more nights and experiences on Airbnb in 2023 than they did in 2022, and 37% more than they did in 2019.

The changing ways of travelers are just one of many factors driving the continued success of this business. The travel resurgence from the doldrums of the pandemic has been well underway for a few years now.

Even as concerns over the flux of discretionary spending are something for investors to bear in mind, the versatility of stays and types of travelers using Airbnb lends a certain level of resilience to this platform that is also worth noting. Airbnb still looks like a rock-solid investment for the long term, and one to perhaps take a second look at before it rockets higher.