This study investigated the potential parameters limiting the stable eCO2RR to formate using In catalyst over 72 h operation. We showed that in order to achieve a stable and efficient eCO2RR, the interrelation between few operational parameters needs to be taken into consideration. In the case studied here being exemplarily for interfacing eCO2RR and bioproduction, a Formate concentration increase in the catholyte and change in conductivity of the catholyte may not directly influence the formate production rate and coulombic efficiency. Yet, they affect the actual cathodic potentials, leading to fluctuations in formate production rate (maximum ± 0.03 mmol h−1 cm−2 at stable operation at each condition) and coulombic efficiency (max. ± 40% at stable operation at each condition) after reaching the certain value of formate concentration and conductivity in the catholyte (ca. 70 mM and 21 mS cm−1, respectively). Therefore, the concentration should be kept below such a value which can be easily achieved by process steering allowing balancing the rates of eCO2RR and microbial consumption. In addition, the stability of the In catalyst needs to be improved in order to operate long-term stable eCO2RR. Confirmed by the increase observed in In corrosion rate at more negative potentials and change in the pH values, H2 generation at the surface could lead to the damage at the surface of the electrode coated by the electrocatalyst. Therefore, the durability of the electrode can be closely related to the electrode potential. One can consider less negative potentials to decrease the catalyst leaching but to increase the HER. However, that would consequently decrease formate production rate from eCO2RR. Alternatively, more C1-compound selective electrodes can be explored and used.