Journey, who was previously chief revenue officer, has taken the role of managing director, international, and will be responsible for expanding the company's presence across EMEA, Latin America and Asia Pacific.
He will be based in the company's London office, which opened seven months ago.
The appointment comes two months after DataXu acquired European real-time bidding specialist Mexad.
Journey said: "As we ramp up our international operations, we will continue our focus on being a neutral, trusted technology partner to brands and their agencies."
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