Fractional Software Engineer for API Integration

Fractional software engineer or full stack developer for a contract role, starting at 10 hours per week with potential for ongoing work. The focus is on API integration, reliable background jobs that retry, scheduled runs, and preventing duplicate invoice creation. You will help shape the repo, build a consistent job structure, create a test harness using saved fake data, enable one-command deployment, set up alerts, and provide a reference integration for future work. Most of the work will involve reviewing pull requests. You will not be client-facing; I handle all client conversations. Please reply in a few sentences: what stack you would build this on, what breaks first when scaling from 2 to 10 clients, and what you are least confident in.