We need backend developer for web app

We need help with backend development for a web app that already has the basic idea planned. The work is mostly related to creating and updating API endpoints, database models, user roles, and server-side logic. The front end will consume these APIs, so the response format should be clean and easy to work with. Expected work: REST API or similar backend structure Database schema updates CRUD logic User authentication and permissions Input validation Clean error responses Webhook or third-party API connection Basic deployment support if needed You should be comfortable reading existing code and improving it instead of rebuilding everything from scratch.