For a decade, we have been hearing about 10x engineers transforming startups. They are often an organization's competitive edge. I have been analyzing various startups, including mine. Conclusion: It is both. Let me argue why.
Instead of looking at the engineers as x or 10x, we should look at the engineers as horizontal or vertical.
In a startup, you need a 10x engineer who can scale horizontally. What that means is that they understand the system as a whole and grasp a variety of concepts as fast as possible. Someone who can jump from setting up load balancers to Kubernetes clusters to tuning databases. You do not have to have knowledge of those concepts in depth, but when a problem arrives in one of these domains, the engineer should have the mindset of diving deep into it and resolving the issue. Generally, 10x horizontal engineers are risk takers and have never say never attitude.
As an organization starts scaling, the system starts getting segregated into pods or domains. And there is often no one person who has domain- or system-wide knowledge. At that point, you need a 10x vertical scaling engineer. The engineer with these characteristics should be able to optimize performances, deep dive into the domain's code, improve the standards, improve the model, algorithms, etc., create processes, or adhere to processes and standards within the organization. Generally, 10x vertical engineers are level-headed, less-risk, more debate-oriented, and more pragmatic and less-radical in nature.
10x-er is not a transferrable characteristic. If an engineer was 10x in one organization, they might not be 10x in another organization with different set-up tools, cultures, and problem statements. A problem arises when an organization that needs a vertical engineer hires a 10x horizontal engineer, and then we have a cultural clash with growth vs. stability.