What happened

Shares of Twilio (NYSE:TWLO) marched 52.7% higher in the first half of 2019, according to data from S&P Global Market Intelligence, as the market celebrated the cloud communication platform's exceptional growth -- both from acquisitions an on an organic basis.

To be clear, Twilio's rise didn't come in enormous post-earnings chunks as is often the case with fast-growing tech names. Rather, its first-half gains were relatively steady, if anything resembling a more pronounced mirror of the S&P 500's impressive 17% gain over the same period.

TWLO Chart

TWLO data by YCharts.

So what

It's also worth noting this incredible momentum was an extension of Twilio's past gains; shares are now up more than 500% from the beginning of 2018, and with good reason.

For one, last quarter's earnings release in early May was Twilio's first as a public company not to mention waning contributions from former top client Uber, which began to transition much of its cloud communications platform development to its own internal engineering teams in 2017. To be sure, Twilio's revenue still skyrocketed 81% year over year in the first quarter of 2019, to $233 million, and rose 60% on an organic basis even after excluding recent acquisitions (notably its late-2018 purchase of cloud-based email services leader SendGrid).

Man in suit drawing glowing line chart indicating gains.

IMAGE SOURCE: GETTY IMAGES.

Better yet, Twilio's dollar-based net expansion rate remained steady last quarter at 146%. Anything above 100% shows renewing clients are spending even more with their refreshed contracts.

And given Twilio's relative outperformance to start the year, the company took the opportunity to raise its full-year guidance, calling for 2019 revenue of $1.102 billion to $1.111 billion (up from $1.065 billion to $1.077 billion previously) and adjusted net income per share of $0.11 to $0.13 (up from $0.08 to $0.11 before).

Now what

Investors should be watching closely, then, to see whether Twilio offers any further revisions to that outlook when it releases second-quarter 2019 results in early August. If it turns out the company has once again underpromised and overdelivered, the stock could easily extend its impressive gains even further.