When some exchange-traded funds (ETFs) come to market, they are labeled as "niche" funds and accused of focusing on too narrow of a market segment to capture the attention of investors. That was the case when the First Trust Cloud Computing ETF (SKYY) debuted nearly six years ago. These days, SKYY has more than proven its mettle. An asset base of nearly $790 million proves as much. Cloud computing is booming, and SKYY remains the only ETF dedicated to this fast-growing corner of the technology sector.

SKYY tracks the ISE Cloud Computing Index, and with cloud computing revenue expected to continue surging in the years ahead, SKYY's credibility as a more focused way to play the technology sector could be enhanced. Since the start of the current bull market, major indexes tracking the broader technology space, internet stocks, semiconductor names and the cloud computing arena have easily topped the S&P 500, with SKYY's underlying benchmark being the winner of that quartet. (See also: Cloud Computing: An Industry in Exponential Growth.)

"From March 9, 2009, to March 31, 2017 (current bull), all four of the technology-related indices featured in the chart outperformed the S&P 500 Index," according to First Trust. "The average annualized total returns for the period were as follows: ISE Cloud Computing Index (+29.95%); Dow Jones Internet Composite Index (+27.72%); Philadelphia Semiconductor Index (+23.00%); S&P 500 Information Technology Index (+22.33%); and S&P 500 Index (+19.28%), according to Bloomberg."

SKYY holds 31 stocks, none of which account for more than 5 percent of the ETF's weight. Tech and internet darlings Netflix, Inc. (NFLX), Facebook, Inc. (FB) and Amazon.com, Inc. (AMZN) combine for about 15 percent of the ETF's roster. SKYY's index has a liberal interpretation of the cloud, as it holds pure-play cloud companies, non-pure-play cloud firms "that focus outside the cloud computing space but provide goods and services in support of the cloud computing space" and technology conglomerates with cloud exposure. (See also: SKYY: First Trust Cloud Computing ETF.)

Cloud computing may not be the first business investors think of when they think of Amazon, but the business is a major driver of revenue growth for the company. Amazon Web Services (AWS), the company's public cloud business, had a fourth quarter run rate of $14 billion. During that quarter, "AWS saw more than $3.5 billion in sales, notching 47 percent year-over-year growth," according to CRN. Amazon's goal for 2016 cloud revenue was $10 billion, but the company easily topped that at $12.2 billion, with an operating profit of over $3 billion. (See also: What Is Amazon Web Services and Why Is It So Successful?)