The researchers of Computer Applications in Science and Engineering department of Barcelona Supercomputing Center develop several simulation codes. Among these Alya, a high performance multiphysics code which solves different engineering problems in the fields of biomechanics, energy, transport (aeronautics, car industry) and smart cities. The code is developed in co-design way, together with the Computer Science department of BSC and hardware vendors like IBM, NVIDIA and NEC. In this talk, we will explain the different parallelization and optimizations techniques we have been implementing and testing to solve the challenging engineering problems we daily face in the department: this involves MPI/IO, hybrid parallelization MPI+X, dynamic load balance, vectorization, heterogeneous computing, multiphysics and multidomain couplings.