Senior Python Developer Needed to Debug an API-Based Registration Script

I am looking for a highly experienced Python developer to diagnose and fix a specific issue in an existing API-based registration script. The script contains a file named register.py, which handles account registrations through the website’s API and processes multiple registrations in parallel. The script was previously working correctly, but it has recently started producing registration failures. I need someone who can carefully inspect the API requests, responses, authentication flow, headers, sessions, concurrency handling, error messages, and any recent changes that may be causing these failures. This is not a project for a beginner or someone who will rely on generic AI-generated answers or experiment with random changes. I need a developer who can read and understand the existing implementation, reproduce the issue, identify the exact root cause, and provide a clean and reliable fix. Scope of Work * Analyze the registration logic inside register.py. * Investigate the failed API requests and responses. * Identify whether the issue is related to authentication, request headers, tokens, cookies, sessions, payloads, concurrency, rate limits, timeouts, or API changes. * Fix only the affected registration functionality. * Test the solution and confirm that registrations work reliably. * Keep the existing parallel-processing functionality stable. Important Restrictions * Only the necessary section of register.py may be modified. * Do not modify any other files or unrelated parts of the script. * Do not restructure or rewrite the full project. * The rest of the system is already working and must remain untouched. * All changes must be targeted, minimal, and clearly explained. Required Experience * Advanced Python development. * Strong experience debugging API integrations. * Experience with HTTP requests, authentication flows, sessions, cookies, tokens, headers, JSON payloads, proxies, concurrency, and error handling. * Ability to analyze API responses and network behavior manually. * Strong debugging and problem-solving skills. * Experience working with complex or highly secured APIs is a strong advantage. Application Instructions Please do not send a generic proposal. In your proposal, briefly explain: * Your experience debugging Python API integrations. * How you usually investigate intermittent API registration failures. * Whether you have experience debugging parallel or concurrent API requests. * Examples of similar issues you have solved. I am looking for someone who can understand the problem quickly and deliver a precise fix without affecting the rest of the project.