Karja received the Young Jazz Talent award in 2014, issued by Jazzkaar and the Estonian Jazz Union. She has a leading position in several collectives including the nine-member group Pae Kollektiiv and the Kirke Karja Quartet among others. With these two groups she has also released albums with her original compositions in 2014 and 2016. In spite of being relatively new, the Kirke Karja Quartet has already performed in almost every European country. In 2017 they were selected to perform at reputable 12points festival.
Karja is a member the Avarus group of musicians, with the Avarus Ensemble as its main output. Besides piano, Kirke also plays various electronic instruments, participating in Lauri Kadalipp Social Jazz, Karl Petti Band and other groups. In 2016, she performed as a soloist at the Estonian Music Days, playing new works composed by Margo Kõlar and Marianna Liik for the Estonian-made electronic organ “Varioola”.
Karja also composes music and creates arrangements. She has written original works for the chamber orchestra Reaalmažoor, Symphony Orchestra of Estonian Academy of Music and Theatre, Avarus Ensemble, the string trio Fresh and many others.