There are several artists/bands called Alexa:
1) Alexa is a rock band from Indonesia. Found on 2007, the band has one album that release June 2009 under Warner Music records.
Official Website : http://www.alexatheband.com
2) Alexa aka Olga Fesenco (born January 3, 1988) is a Moldovan pop artist that has taken several times part in the Moldovan national final of the Eurovision Song Contest. In 2008 her song was "We Are One" and in 2009 "(A Flight) to the Light".
3) Alexa is a Hungarian singer (Eördögh Alexa)