  We performed a high energy resolution ARPES investigation of over-doped
Ba0.1K0.9Fe2As2 with T_c= 9 K. The Fermi surface topology of this material is
similar to that of KFe2As2 and differs from that of slightly less doped
Ba0.3K0.7Fe2As2, implying that a Lifshitz transition occurred between x=0.7 and
x=0.9. Albeit for a vertical node found at the tip of the emerging
off-M-centered Fermi surface pocket lobes, the superconducting gap structure is
similar to that of Ba0.3K0.7Fe2As2, suggesting that the paring interaction is
not driven by the Fermi surface topology.
