Contactually

Company: CRM for professional services—helps real estate brokerages, law firms, accounting firms and any sales-related professional stay engaged.
Revenue: $4M
Employees: 52, including the founding fathers and two dogs, Ellie and Astro (pictured).
Growth: 125% in revenue, 100% in head count
Reason for growth: Nailed product market fit; riding a big market focus on customer-centric cultures; and unlocked vast amounts of data via the move to the cloud and the BYOD movement. 
Top customers: Major brokerages, including Coldwell Banker and Keller Williams. 
Recent news: Added major key VPs.
Most people don’t know: Contactually raises funds for Roots for Development, a community investment organization, and sends a team every year for on-site business training in Haiti. The company's five (and counting) office dogs have their own place on the org chart.

OBXtek

Company: IT and management services for the federal government.
Revenue: $64.4M
Employees: 480
Growth: 72% in revenue, 92% in head count
Reason for growth: Aggressively going after business in US government services and focused on building the company’s experience in growing sectors like cybersecurity and IT consolidation. Seeing company growth despite federal spending cuts.
Top customers: State Department, Social Security Administration and Air Force.
Latest news: Awarded US Naval Academy contract to provide functional and technical program support to Midshipmen, faculty and leadership for hardware and software on USNA devices. 
Most people don’t know: Company’s charitable work includes working with the Na Koa Annual Canoe Regatta to promote awareness of the Wounded Warriors Foundation. And yes, the OBX in the company’s name stands for the Outer Banks of North Carolina. The company has a beach house in Corolla, which is available free of charge to employees who have gone above and beyond in support of the company and its customers.

Tenable Network Security

Company: Continuous network monitoring.
Employees: Over 500, including CEO Ron Gula (pictured).
Growth: 50% in revenue.
Reason for growth: Next-generation security technology and intense focus on customer relationships.
Top customers: Large corporations, not-for-profit organizations and public sector agencies like the DOD.
Latest news: Awarded Frost & Sullivan’s 2015 Technology Innovation Award and added Ron Kaiser and Michael Capellas to the board. 
Most people don’t know: Because of Tenable’s strong relationship with the DOD, most people think the company is a government contractor. But most of its work is done for Fortune 500 companies.

Did you miss Part 1, Part 2 and Part 3 of the Fastest-Growing Companies series? You're also invited to help celebrate the Fasting-Growing Companies at a party on Oct. 20 at 1776-Crystal City.