Senior Full-Stack Engineer — CRM Stabilization & Platform Migration (PT-WW)

Role Overview

We are seeking a skilled Senior Full-Stack Engineer to stabilize, secure, and potentially migrate a custom practice management platform utilized by a physiotherapy and personal training business. This platform is integral in supporting various operations such as scheduling, booking, invoicing, payroll, client communication, reporting, clinical records, payments, and client-facing functionalities. Built using React and Base44, it features custom serverless functions, automations, payment integrations, and role-based access controls. The main objective is to review the existing system, address backend and security issues, and provide recommendations on whether to maintain the current platform or migrate to a more conventional architecture.

Responsibilities

• Conduct a comprehensive review of the existing React and Base44 application architecture.
• Validate previous technical audit findings and identify additional risks.
• Diagnose and resolve backend bugs and unreliable workflows.
• Enhance authentication, authorization, and role-based access controls.
• Audit and improve database permissions and row-level security.
• Re-enable and validate secure Square webhook verification.
• Eliminate hardcoded configuration, IDs, and sensitive values from the source code.
• Optimize secrets management and environment configuration.
• Review and refine serverless functions, scheduled automations, and elevated service-role access.
• Enhance application stability through improved error handling, logging, monitoring, and graceful fallbacks.
• Evaluate the feasibility of maintaining the system on Base44 or migrating to an external hosting and backend platform.
• Develop clear architectural recommendations covering effort, risk, cost, and sequencing.
• Design and potentially execute a phased migration of backend, database, authentication, file storage, and automations.
• Support testing, production rollout, data migration, and post-launch stabilization.
• Advise on future white-label, multi-tenant, and client mobile application requirements.

Required Skills

• Strong full-stack development experience with modern JavaScript or TypeScript.
• Advanced proficiency in React.
• Experience in building or maintaining serverless backend systems.
• Comprehensive understanding of authentication, authorization, and role-based access control.
• Experience in securing APIs, payment workflows, and webhook integrations.
• Expertise in database design, access controls, and data migrations.
• Proficiency in debugging and restructuring complex or rapidly built applications.
• Experience with cloud-hosted applications, environment configuration, secrets management, and monitoring.
• Ability to assess existing architecture and make practical build-versus-migrate recommendations.
• Strong capacity for independent work and effective communication of technical findings to non-technical stakeholders.

Nice to Have

• Experience with Base44 or similar managed or low-code platforms.
• Familiarity with Deno or Node.js serverless functions.
• Experience with Square payments.
• Experience migrating applications from platforms like Firebase, Supabase, Bubble, or Retool.
• Knowledge of PostgreSQL, managed authentication providers, and object storage.
• Familiarity with multi-tenant SaaS architecture.
• Experience with systems handling sensitive data such as healthcare, clinical, payroll, or financial systems.
• Experience with React Native, Flutter, or progressive web applications.
• Familiarity with AI-generated or “vibe-coded” applications.