(Veteran tech columnist Jon Markman publishes Strategic Advantage, a guide to investing in the great digital transformation of society. Click here for a two-week trial.)

Roku Inc. ( (ROKU) - Get Report) is one of the hottest technology stocks anywhere. Investors love the company’s fast growth and transformative business. But competition is coming from an unlikely source: Google and its own fast-forward TV ambitions.

Investors are seeing none of that today. Roku shares opened sharply higher after the company announced Wednesday evening that it was bringing HBO Max to its streaming platform.

The deal might be the last hurrah for a while.

Time Warner launched HBO Max in May. The streaming service of the AT&T ( (T) - Get Report) unit is an important part of the future of the big entertainment business. As media consumption moves further away from the physical world of theatres, content producers have begun shifting their businesses models toward digital distribution. Analysts believe that some combination of paid subscriptions and advertising revenue should support several large players.

Roku is a unique platform. The company reinvented television for the digital era by acting as a neutral gatekeeper for its big media partners. In some cases Roku takes a piece of the subscription price, such as its agreements with Disney ( (DIS) - Get Report) and Netflix (NFLX). In other instances, such as YouTube and Peacock, the new streaming business from Comcast ( (CMCSA) - Get Report), Roku sells additional targeted advertising around the content.

The appeal of Roku to media partners is reach. The San Jose, Calif.-based media platform has built a tidy business catering to media consumers that have cut the cord with traditional linear TV. With its dead simple user interface and access to over 4,000 media applications, cable TV ditchers flocked to Roku. In November, executive said the platform had 46 million active monthly users.

And managers have been careful to build out other business verticals.

Two years ago the company launched the Roku channel, a free TV offering where members can watch content with commercials. For cord cutters, free is always better.

Meanwhile Roku managers continue to add hardware partnerships. Roku set top boxes, dongles and license agreements with TV makers put the platform in front of millions of new customers. Buyers of TCL and Hisense televisions, for example, get Roku as their smart TV operating systems.

All of this platform momentum put Roku managers in a powerful position. Content producers like YouTube, Netflix (NFLX), Disney (DIS), Peacock (CMCSA) and Apple (AAPL) had to be on the platform to reach cord cutters.

HBO managers resisted. They felt Roku was demanding too much advertising inventory. That is until HBO managers caved Wednesday. A Roku press release noted the importance of reaching platform members ahead of the release of Wonder Woman, a big budget film set for release Christmas day.

All of this seems like good news for Roku. The company has a dominant platform with scale, leverage over content providers and hardware partnerships that ensure a steady stream of new members.

The problem is Google TV.

Last month the Alphabet ( (GOOGL) - Get Report) unit rebranded its Chromecast hardware as Google TV. Chromecasts are dongles that mount directly to the HDMI port on television sets. They allowed users to cast media playing on their smartphone directly to the big screen.

Google TV has all of the best aspects of Chromecast but it also brings an operating system tuned by Google Search. Despite its modest $50 price, Google TV is 4K ready and has most of the features of Roku boxes that cost up to twice as much. Google TV interface looks a lot like Android, except for TVs.

That should worry Roku shareholders.

The company is suddenly competing with Alphabet for cord cutters, hardware partners and content providers. On the latter point, Google TV came with access to Disney+, Netflix, Peacock and HBO Max at launch. Wednesday the company announced that Apple Plus is coming in early 2021.

However the killer feature of Google TV is Alphabet’s machine learning prowess and enormous scale. All of the user’s streaming services are searchable from the home screen. Google algorithms make recommendations based on viewing habits. And YouTube Movies integration means there is plenty of free content to watch, too.

Roku shares are up 148% in 2020. The stock trades at 26x sales. Undoubtedly investors are paying up for its past heady growth. Sales grew 52% in 2019 to $1.1 billion.

Investors should think twice and hit pause before jumping into Roku stock at current levels.