A question I come across often is whether or not a Scrum Master (or for that matter an Agile Coach) should have extensive knowledge in the business and/or technical domain in which the team they are working with is engaged in. I find that many people believe the Scrum Master should be an SME or else they will not be able to provide any (or as much) value to the team they are working with. I find just the opposite is true. When a Scrum Master is a knowledgeable expert they tend to engage in command and control activities even though they are often exceedingly nice about it. They tend towards telling the team what to do and how to do it vs. being exclusively focused on how well everyone is working together (including the organization around the team and with the customers, stakeholders, etc.). There is no doubt that a Scrum Master who is a domain expert is going to be able to give some constructive input however they are also at a high risk of giving destructive input, input that erodes the team’s ownership of their work or undermines the Product Owner’s authority.
The role of Scrum Master is utterly unique in corporations. There is no other role quite like it and I find that those who excel at the role (and hence work with teams that excel in their roles) focus on how each individual is doing and how the team is doing together. They are focused on the personal and interpersonal dynamics which lead to great work, each individual giving their all to the team and the team giving their all to the product. Being agnostic about the nature of the work itself, they allow themselves to focus on the people and the organization, on removing and resolving and escalating impediments at the team level and at the organizational level. They get to focus on the culture and the values and principles that drive it. Instead of the ‘what’ or the ‘why’ or even the ‘how’ of the work, they are simply focused on ‘how well’ it is all going, and this focus is invaluable even though at times it seems invisible. Without someone focused in this way, the team just has one more contributor who may or may not be truly adding value, they may even be taking it away.
So my recommendation is always to look for the right people to be Scrum Masters, those with the characteristics that will truly drive the team forwards towards perfection (even though they will never reach it), and someone who can help drive change in the larger organization. For this is where the true value of the Scrum Master lies, not in domain expertise.