The network vendor Arista Networks presents a rare characteristic among high-growth tech companies: It's been posting significant profits over the last several years. The company took advantage of the shift from traditional locally hosted networks to cloud networks. But the company's expansion into other markets may drag down its impressive performance.

A significant cost advantage

Arista's business consists of selling software and network hardware -- routers and switches -- that equip data centers. The company developed flexible solutions that address the superior customization and performance that cloud networks command compared to legacy networks.

As a result, and thanks to the growth of cloud computing, the company increased its trailing-12-month (TTM) revenue to $2.36 billion, from $71.7 million in 2010. With its growing scale, the company's revenue growth decelerated to 21.3% during the first half of the year compared to 30.7% and 45.8% in 2018 and 2017, respectively. But the company's strong double-digit revenue growth remains impressive. 

Cloud computing

Image source: Getty Images.

In contrast, Arista's competitor Cisco (NASDAQ:CSCO) posted mid-single-digit revenue growth over the last several quarters. And Juniper (NYSE:JNPR), another competitor, reported declining revenue. Cisco's and Juniper's broader portfolios, which include legacy network components, explain their underperformance relative to Arista.

Many other tech companies have been posting revenue growth in the same range as Arista, but none has matched Arista's 30%+ GAAP operating margin (see table below). 

Arista's cost advantage owes to its customers' large sizes. Management confirmed during its last earnings call that what it calls "cloud titans" -- giant cloud companies -- constituted the company's largest segment. For instance, Microsoft represented 27% and 16% of Arista's revenue in 2018 and 2017, respectively. In addition, Arista also serves other huge companies such as service providers and financial institutions.

Since Arista is increasing its revenue primarily from its existing large customers, its sales and marketing expenses have remained low, at 8.6% of the company's revenue during the first half of this year.

In contrast, many high-growth tech companies such as the ones listed below need their sales and marketing expenses to exceed 44% of their revenue to acquire many smaller customers. As an illustration, Palo Alto's TTM revenue exceeds Arista's revenue by only 22.7%,, but Palo Alto's 60,000+ customers at the end of calendar year 2018 eclipsed Arista's 5,500+ customers.

Company TTM Revenue Growth Operating Margin Most Recent Quarter Sales & Marketing As a Percentage of Revenue
Arista Networks (NYSE:ANET) 24.5% 33.3% 8.7%
Palo Alto Networks 27.5% (2.11%) 44.9%
Fortinet 19.9% 12.7% 43.4%
Splunk 37.7% (24.6%) 62.7%

Data source: Arista Networks, Palo Alto Networks, Fortinet, and Splunk, based on their respective current fiscal years. YOY = year over year. 

Arista is expanding outside of its core business

Given its success in cloud data centers, Arista is diversifying into other network areas. Last year, management announced the company's expansion into the campus segment, which means the company's network solutions will also cover smaller local networks. And the company recently integrated wireless capabilities into its portfolio.

From an operational perspective, these decisions make sense. Cloud, campus, and wireless networks use similar technologies. Besides, customers may appreciate consolidated management systems, and Arista will profit from cross-selling opportunities.

But Arista must ramp up its sales and marketing efforts to reach a higher number of smaller customers in the campus segment. As a result, management indicated during its last earnings call that Arista's sales and marketing expenses would gradually increase to 10% of the company's revenue.

Arista's forecasted sales and marketing costs seem still low compared to legacy network vendors. Cisco's and Juniper's sales and marketing expenses represented 18.4% and 21.7% of their respective revenue during their current fiscal year. But as Arista expands into legacy network vendors' markets such as campus and wireless, Arista's sales and marketing expenses should increase, drawing closer to Cisco's and Juniper's costs over the long term.

No margin of safety

The market values Arista at trailing-12-month price-to-sales and P/E ratios of 7.4 and 26.5, respectively. These numbers indicate that investors expect Arista to sustain its solid growth and its high operating margin. But given the potential decline of the company's operating margin because of its expansion outside of the cloud data centers, Arista's valuation doesn't offer any margin of safety.

Thus, despite Arista's impressive results, prudent investors should stay on the sidelines unless the company's shares drop significantly.