Expert Developer: Square POS & Submatic Integration with Knack EMR (Webhooks/API)

Job Overview We are seeking an experienced Systems Integrator and Backend Developer to perform a comprehensive "deep dive" and cleanup of our current technical ecosystem. We currently utilize Square POS in conjunction with Submatic (our membership and subscription management app). Square Our goal is to optimize the current setup, eliminate redundancies, and build a reliable, efficient data pipeline between Square/Submatic and our custom Electronic Medical Records (EMR) system built on Knack. A deep understanding of Square’s API architecture and webhooks is absolutely critical for this project. If you are someone who enjoys auditing existing systems, stripping out the noise, and building clean, automated workflows, we want to talk to you. Key Responsibilities System Audit & Cleanup: Take a deep dive into our current Square POS and Submatic configuration to identify inefficiencies, data mismatches, or sync errors. Scrub the system to ensure clean data hygiene. Custom API Integration: Build a reliable integration connecting Square POS / Submatic data workflows directly to our custom Knack EMR platform. Webhook Implementation: Set up and configure Square webhooks to trigger real-time actions and state changes within the Knack EMR (e.g., membership updates, transaction completions, customer profile syncs). Workflow Optimization: Ensure that membership statuses from Submatic flow smoothly into Square POS for front-of-house staff while concurrently updating patient records in Knack. Testing & Documentation: Thoroughly test the integration across all edge cases (canceled memberships, failed payments, new walk-ins) and provide lightweight documentation of the API map. Required Skills & Qualifications Square Ecosystem Expertise: Advanced knowledge of Square POS, Square Customer Directory, and Square’s API catalog (specifically Orders, Customers, Subscriptions, and Payments APIs). Webhook Mastery: Proven experience working with Square webhooks, payload handling, and asynchronous event processing. Database & No-Code/Low-Code Platforms: Deep familiarity with Knack database structures, Knack's native API, and managing data objects within a relational database. Integration Middleware (if applicable): Proficiency in using Make.com, Zapier, or building custom Node.js/Python serverless functions to handle the payload transformation between Square and Knack. Data Hygiene Focus: A meticulous eye for identifying duplicate records, orphan data, and broken synchronization loops. Nice-to-Haves Prior experience working specifically with the Submatic membership application. Background working in healthcare operations or familiarity with safeguarding data privacy workflows within custom EMRs. Project Type & Budget Project Type: One-time project with potential for ongoing maintenance/troubleshooting. Project Scale: Mid-to-Large (requires a thorough discovery phase followed by execution). Engagement: Hourly or Fixed-Price (Milestone-based). Please provide your estimated timeline and approach in your proposal. How to Apply To be considered, please reply with: A brief summary of your experience working with Square’s API and Webhooks. Have you worked with Knack or Submatic before? If not, briefly explain how you would approach mapping data into a custom database environment. Your availability to start and your preferred structural approach for auditing an existing setup before writing code. (Please start your proposal with the word "SYSTEMS" so we know you read the full description.)