A metallic-ceramic joint for a turbo-compressor spool is disclosed. A temperature-limited joint is moved from outside the bearings to between the bearings and near the center of the shaft joining the turbine and compressor. This placement can lower the temperature at and around the joint and reduces the sharp gradient (and associated thermal stress) naturally occurring between the turbine rotor and the cooler joint. The bearing closest to the compressor can be an oil bearing and the bearing closest to the turbine an air bearing. The bearing closest to the compressor and the bearing closest to the turbine can both be an oil bearing. The bearing closest to the compressor and the bearing closest to the turbine can both be an air bearing. Moving the metallic-ceramic joint between the bearings can provide sufficient isolation to enable the all-air bearing solution.