Komagataella phaffii (formerly Pichia pastoris) is a well-known fungal system for heterologous protein production in the context of modern biotechnology. To obtain higher protein titers in this system many researchers have sought to optimize gene expression by increasing the levels of transcription of the heterologous gene. This has been typically achieved by manipulating promoter sequences or by generating clones bearing multiple copies of the desired gene. The aim of this work is to describe how these different molecular strategies have been applied in K. phaffii presenting their advantages and drawbacks.