Shares of Luxoft Holding Inc. (NYSE: LXFT) were down 21.3% as of 11:30 a.m. EDT Thursday after the software development company announced strong quarterly results, but followed with light guidance.On the former, for Luxoft's fiscal fourth-quarter ended March 31, 2018, revenue climbed 14.1% year over year to $232.9 million. That translated to adjusted (non-GAAP) net income of $20.5 million, or $0.59 per diluted share, down from $21.5 million, or $0.63 per share in the same year-ago period.