I once had a side-gig where I advertised auditing out-sourced coding. Basically hundred-k loc reviews. It was fun, but word got around that I was good at it (uncovered security issues, reduced costs by finding things that could be optimized, etc). It’s on my resume, and that’s how interviewers know I can do the job. I can tell “war stories” about the code I reviewed, how I handled engineers that tried to obfuscate the code, etc.