Twilio  (TWLO) - Get Twilio, Inc. Class A Report shares were down roughly 3.3% at $111.50 in after-hours trading after the company topped fourth-quarter revenue estimates but fell flat on earnings. 

The cloud communications firm reported total revenue of $204.3 million for the December quarter, representing a year-over-year increase of 77%. It had previously guided for total revenue between $183 million and $185 million.

Twilio reported non-GAAP income per share of 4 cents, while analysts polled by FactSet had been expecting earnings per share between 3 cents and 10 cents a share.

"The power of our platform model was evident in our results once again, as Q4's exceptional results capped off an incredible 2018," said Twilio CEO Jeff Lawson in a press release.

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Twilio builds communication-as-a-service APIs and other tools, which help businesses combine various communication and customer services, including phone, videoconference and SMS, into one system. This month, Twilio closed its acquisition of SendGrid, an email delivery service, which brings email into its portfolio.

The company's fourth quarter results continue a trend of strong revenue growth at Twilio: Its total revenue for the full year 2018 was $650.1 million, up 63% from the previous year. Among the critiques of Twilio's stock, however, is that its revenue is too reliant on certain marquee customers like Uber, which at one point made up 20% of its revenue. 

In an interview on Tuesday with Real Money, TheStreet's premium site for active investors, Twilio CEO Jeff Lawson and COO George Hu discussed Twilio's recent progress in breaking out of a tech and app-heavy customer base. ""We've talked a lot about engaging new customers and diversifying our customer base...we now have customers like E*Trade (ETFC) - Get E*TRADE Financial Corporation Report , U-Haul and more," Hu said.

Bullish analysts point to Twilio's positioning in the growing cloud services market as a predictor of future growth in the stock. For the March quarter, Twilio guided for total revenue between $222 million and $225 million. For the full year 2019, it guided for revenue between $1.065 billion and $1.077 billion, and non-GAAP net income per share between $.08 and $.11.

"They're really the foundation that are enabling real time communication between both the business, customers, and clients," said AAP portfolio analyst Jeff Marks on a call with investors in January. 

Twilio's stock is up roughly 33% since the beginning of this year. It closed at $115.29 a share ahead of the report.