A two stage Fluid Catalytic Cracking process and an apparatus for simultaneous production of light olefins such as ethylene and propylene and middle distillate range hydrocarbons, wherein a first flow reactor, preferably a downer and a second flow reactor, preferably a riser are operating at varying reaction severities using different catalyst systems with the regenerated catalyst entering the reactors inlet through independent regenerators. Mild cracking of the fresh feedstock is carried out in the first flow reactor of short residence time and the effluent of first flow reactor is separated in an intermediate separator/fractionator followed by re-cracking of the C4 hydrocarbons and naphtha range hydrocarbons, preferably C5-150° C. from the second product separation section and unconverted hydrocarbons (370° C.+) of first flow reactor, in the second flow reactor at higher severity employing different catalyst system.