API Developer – Bullhorn/ActiveCampaign Integration for B2B Marketing Automation

We are seeking an experienced API developer to architect and implement a robust, bidirectional integration between Bullhorn CRM/ATS and ActiveCampaign, our marketing automation platform. This integration will ensure accurate, real-time synchronization of lead and contact data, enabling seamless alignment between marketing and sales operations.

Scope of Work
Develop a secure middleware layer that wraps Bullhorn and ActiveCampaign REST APIs
Enable lead/contact sync with key fields (name, email, phone, company, tags/lists)
Support bidirectional synchronization: updates in one system are reflected in the other
Map and handle custom fields (e.g., lead stage, status, source, job role)
Implement webhook orchestration and polling fallback for near–real-time updates
Integrate retry logic with backoff, dead-letter queues, and structured logging
Ensure scalability to handle high lead volumes and future extensibility
Provide audit-ready documentation and test harnesses for QA and stakeholder handoff

Required Skills & Experience
Proven experience building API integrations for CRM and marketing automation platforms
Strong knowledge of REST APIs, JSON, and development in Python, Node.js, JavaScript, or PHP
Familiarity with OAuth 2.0, Bullhorn REST API, and ActiveCampaign API
MUST HAVE: Experience setting up API integrations in marketing automation environments (not just general web development)
Experience with Zapier, Make, or other middleware tools as fallback workflows
Strong communication skills and ability to work independently

Preferred Architecture
Middleware layer that wraps both REST APIs and centralizes sync logic
Webhook triggers and polling fallback for update detection
Configurable mapping layer for field transformations and validation rules
Deployment via AWS Lambda, ECS, or Vercel depending on scale and latency needs
Structured logging, correlation IDs, and error resilience mechanisms

Deliverables
Fully functional bidirectional integration between Bullhorn and ActiveCampaign
Test cases demonstrating correct data sync in both directions
Data schema for contact field mapping and transformation logic
Secure deployment with credential management
Documentation: API endpoints used, field mapping, troubleshooting guide, and QA handoff materials

Budget
We are open to proposals depending on experience and approach. Please include:
Estimated hours and cost for a basic one-way sync
Estimated hours and cost for a full bidirectional sync with custom fields and error handling

Timeline
Target completion: 4–6 weeks from project start