A Google Geocoding API developer integrates Google's Geocoding API into websites or applications to convert addresses into geographic coordinates. They use these coordinates to place markers on maps or position the map. They can also reverse geocode, converting geographic coordinates into a human-readable address. Their responsibilities include understanding API integration, debugging, and ensuring the functionality aligns with the project's requirements. They work closely with other developers and stakeholders to enhance user experience by providing accurate location data. They must also manage and monitor API usage to avoid surpassing usage limits, handling API keys securely.