Full Stack Developer Needed for Custom Mobile and Web Applications

We operate a multi-location car wash business utilizing a centralized POS system. We are seeking an experienced freelance or contract developer to lead a custom API and website integration project. This project will establish a scalable, secure integration between the POS and multiple digital platforms, including internal mobile apps, internal tools, customer-facing mobile app, and a customer-facing website. We have existing mobile and web applications that can be reviewed as examples and are planning on documenting as much as possible about the current system setup. This role requires strong experience in API design, system integrations, and WordPress plugin development, along with the ability to collaborate with non-technical stakeholders. The goal is to create a single POS-integrated API layer that can power: • Internal location tools (mobile and web apps) • Site Operations • Membership Enrollment • A customer mobile app • Integrating API connection to the POS via plugin or other integration to our website (WordPress based) Work is split into phases to reduce risk and validate integrations early. Key Responsibilities • Design and implement custom API integrations between our POS system and website • Develop and launch internal use site operations and membership management mobile and web apps, complete with backend portal/gateway for employee management. • Develop and maintain custom WordPress plugins to serve as the integration layer • Integrate payment gateways and membership systems securely • Support user registration, recurring memberships, and membership management • Advise on technical architecture and best practices • Provide clear technical documentation for long-term maintainability • Coordinate with design and marketing teams during website redevelopment Required Experience Strong full-stack development background Expert-level knowledge of: REST APIs, JSON, PHP, Ruby React or Angular API authentication and authorization (OAuth) Secure payment handling and PCI compliance Knowledge of security concerns and best practices Ideally, some knowledge of web or visual design, plus user experience best practices Proven experience building: Custom WordPress plugins API-driven integrations with third-party systems (POS, CRM, payments, etc.) Enterprise level mobile and web applications Ability to communicate clearly with non-developers Strong documentation habits Hourly or project phase rate is negotiable based on experience and estimated timelines.