I believe the open systems db2 team was mainly based out of Canada, but I don't think you were really honestly asking that question.
However, in case I can share a bit that I may know some small amount about is that the area that the author worked on is quite well-known to IBMs db2 customers. The ability for db2 to self-tune has put it ahead of sql server, oracle and others in some ways, for decades. While the author clearly got hired and found himself in a good niche at IBM and grew there, IBMs database teams have definitely hired and sustained people from various backgrounds because the work can be challenging and rewarding.
I'm saying this because one of my uncles maintained the lock manager in the mainframe db2 codebase for most of a couple of decades including being there at the time the author mentioned, working on sysplex and parallel sysplex, and he entered that gig without a particular interest in databases as he told it. But he really did take to assembly and production code maintenance
However, in case I can share a bit that I may know some small amount about is that the area that the author worked on is quite well-known to IBMs db2 customers. The ability for db2 to self-tune has put it ahead of sql server, oracle and others in some ways, for decades. While the author clearly got hired and found himself in a good niche at IBM and grew there, IBMs database teams have definitely hired and sustained people from various backgrounds because the work can be challenging and rewarding.
I'm saying this because one of my uncles maintained the lock manager in the mainframe db2 codebase for most of a couple of decades including being there at the time the author mentioned, working on sysplex and parallel sysplex, and he entered that gig without a particular interest in databases as he told it. But he really did take to assembly and production code maintenance