Composite structures are widely used for thin-walled components due to their high specific strength and stiffness. For load introduction elements, however, metallic brackets are typically used due to the three dimensional stress states. Optimizing such a bracket, e.g. by means of topology optimization, might reduce the performance of the composite shell. The current talk will show that for the optimization of a load introduction region, the whole assembly of bracket, composite shell and their interface must be considered. We present an approach for the simultaneous topology optimization of an isotropic (e.g. metallic) part, the layup optimization of a composite part, and the search for the optimized position of the joints between the two parts. The design variables considered in this holistic optimization approach are hence the (pseudo) densities of the isotropic parts, the fiber orientations in each element and ply of the composite shell, as well as the positions of the reference points of the joint nodes. Since a gradient-based optimization algorithm is employed, the gradients of objective and constraint functions are derived with respect to all design parameters. The results show that an individual optimization of one part may be critical for the performance of the connected part and hence, worsens the overall performance. The proposed simultaneous optimization approach however allows to efficiently improve the performance of the assembly as a whole.