Solid-state batteries (SSBs) that pair a lithium metal anode with an inorganic solid electrolyte hold promise to simultaneously improve the energy density, power density and safety as compared to conventional lithium-ion batteries. However, the development of SSBs is confronted with challenges including electrochemical-transport-mechanics interplay and morphological instability at various solid-solid interfaces. Toward achieving practical SSBs, gaining a fundamental understanding of the mechanistic interactions and systematically correlating those to interface stability and performance is critical. In this presentation, we delineate the distinct asymmetry in the electrochemical-mechanical interaction, limiting mechanisms and interface response during operation. The mechanistic role of heterogeneities that underlie at solid-solid interfaces on the stress-transport-kinetics interplay will be discussed.