A growing Sonoma online wine retailer that specializes in "flash sales," or limited-time deals, has acquired a Southern California competitor.

Good Company Wines, the parent company of members-only wine sales website Invino.com, acquired San Diego-based Internet retailer CellarThief.com on Friday. Financial terms were not disclosed.

"It gives us the ability to be able to reach different consumers, and the ability to really grow our base of business with a different voice, and a different channel," said Tony Westfall, co-founder and CEO of Good Company Wines.

Westfall and his wife, Danielle, launched Good Company Wines in 2009. The umbrella company also owns entities that specialize in wine importing and exporting, distribution and warehousing.

"We've always been big fans of e-commerce for wine," Tony Westfall said. "I think there's been a lack of penetration for alternate channels of doing business in the wine business."

The fashion industry developed the concept of "private sale" websites a decade ago as a way to discreetly sell luxury goods at discount prices, Westfall said.

The concept also works well for wineries that seek to clear inventory but don't want to advertise that their $50 wine recently sold for $30. By selling the wine on a website where a login is required, it's less likely to attract widespread notice and impact future pricing.

"It offers wineries brand protection," Westfall said. "It's not really leaving tracks anywhere on the Internet."

The purchase of CellarThief.com enables Good Company Wines to expand its reach. Invino.com targets aspirational drinkers who like to try new wine at a good value, Westfall said. It offers small, niche producers and well-known brands, and the average sale price is around $20 a bottle.

Westfall said he plans to upgrade the quality of the wines at CellarThief.com.

CellarThief.com was about a tenth of the size of Good Company Wines in terms of revenue, Westfall said. The four employees who worked at CellarThief.com, which included the founders, did not stay on in the assets-only sale. Good Company Wines has about 25 employees, plans to hire an additional five, and hopes to double its workforce next year, Westfall said.