Salesforce Apex Custom API Sync

I need a developer who can build a clean, well-tested Apex solution that keeps Salesforce records in step with an external CRM through our own REST-style APIs.

Here’s the scenario: the external CRM is already exposing endpoints for accounts, contacts, and related activities. Your task is to write the Apex callouts, authentication flow, and scheduling logic that will pull and push changes so data stays consistent on both sides in near-real time. The integration is strictly custom API based—no middleware or AppExchange packages—so you should be comfortable writing raw HTTP callouts, handling JSON, and managing governor limits.

Key points
• Primary goal: bidirectional data synchronization
• Source systems: Salesforce ↔ external CRM (no ERP or marketing tools in scope)
• Code requirements: Apex classes, triggers or Platform Events where appropriate, and comprehensive test coverage (≥75%)
• Must include retry logic, error handling, and clear inline documentation
• A concise setup guide so my admin team can deploy to production without surprises

If you have delivered similar custom API integrations before and can work remotely on a mutually agreed schedule, let’s get this started.