The epic third person plural of kei=mai (perfect with present sense) is glossed with its Attic counterpart. Same entry already in Hesychius (kappa1958) and in a scholion on Homer, Iliad 11.659, where the headword occurs (web address 1). The Etymologicum Gudianum (p. 309) discusses this form, calling it an Ionic present tense (there are further instances in Herodotus). The alpha comes from a dialectal treatment of vocalic n; see Smyth §791D (web address 2).
Besides 11.659 (above), the form ke/atai occurs also in Iliad 11.826, 16.24, 19.203. For other forms of this verb, see kappa 1473, kappa 1474.