What is the most efficient beam design?

Could you please elaborate on what constitutes the most efficient beam design? What factors should be considered in determining its efficiency? Is it solely based on structural strength or does it also include material usage, cost, and sustainability? How does the shape and size of the beam affect its efficiency? Are there specific engineering principles or theories that guide the design process? Additionally, are there any innovative techniques or materials that can enhance the efficiency of beam designs? Thank you for your insights on this matter.