I’m rebuilding a web application whose backend currently mixes legacy PHP with newer modules. The stack centres on PHP (latest stable) and a MySQL database, and I need an experienced backend developer who can confidently step into an evolving codebase while also creating fresh, well-architected components. Here’s what I need tackled: • API development – design and implement RESTful endpoints that plug seamlessly into the existing logic and any new features we add. • Database optimisation – review schema, refactor queries, add indexes, and benchmark improvements so we can see tangible speed gains. • User authentication system – build a secure, token-based solution that fits the current login flow and is flexible enough for future SSO or OAuth expansion. Because we’re working with a combination of old and new code, part of the job will involve auditing what’s already there, refactoring where it makes sense, and documenting your changes clearly so maintenance stays straightforward. Clean, commented code, Git-based version control, and concise commit messages are expected. If you’ve delivered high-performance PHP/MySQL backends before and enjoy turning complex, hybrid codebases into fast, reliable systems, I’d love to collaborate with you on this upgrade.