"Serves as" is a common phrase used when describing a particular role or function of something or someone. However, there are several other synonymous words or phrases that can be used in its place. Such as, acts as, functions as, operates as, carries out the role of, holds the position of, plays the part of, fills the role of, and provides the function of. The use of these synonyms can help to add variety to one's writing or speaking, and can even add clarity in some cases. So, whether it's in a formal or informal setting, there are plenty of alternatives to "serves as" that can be used effectively.