  We have used scanning micro x-ray diffraction to characterize different
phases in superconducting K$_{x}$Fe$_{2-y}$Se$_2$ as a function of temperature,
unveiling the thermal evolution across the superconducting transition
temperature (T$_c\sim$32 K), phase separation temperature (T$_{ps}\sim$520 K)
and iron-vacancy order temperature (T$_{vo}\sim$580 K). In addition to the
iron-vacancy ordered tetragonal magnetic phase and orthorhombic metallic
minority filamentary phase, we have found a clear evidence of the interface
phase with tetragonal symmetry. The metallic phase is surrounded by this
interface phase below $\sim$300 K, and is embedded in the insulating texture.
The spatial distribution of coexisting phases as a function of temperature
provides a clear evidence of the formation of protected metallic percolative
paths in the majority texture with large magnetic moment, required for the
electronic coherence for the superconductivity. Furthermore, a clear
reorganization of iron-vacancy order around the T$_{ps}$ and T$_c$ is found
with the interface phase being mostly associated with a different iron-vacancy
configuration, that may be important for protecting the percolative
superconductivity in K$_{x}$Fe$_{2-y}$Se$_2$.
