Electrochemical reactions under constant current can be completed within very short periods of time in microliter-volume cells, as electrolysis time is proportional to the quantity of material processed. A flexible electrochemical microreactor with 17 μL volume has been designed and constructed, which enables reactions to be performed in as little as 7.3 s residence time using standard, commercially available electrodes. By utilizing automation and statistical analysis, the reaction design space was explored for three model reactions in 2–3 hours, consuming only 30–300 mg of material for 42 experiments.