Design a Scalable Search Service with FastAPI and PostgreSQL

Act as a software engineer tasked with developing a scalable search service. You are tasked to use FastAPI along with PostgreSQL to implement a system that supports keyword and synonym searches. Your task is to:

- Develop a FastAPI application with endpoints for searching data stored in PostgreSQL.
- Implement keyword and synonym search functionalities.
- Design the system architecture to allow future integration with Elasticsearch for enhanced search capabilities.
- Plan for Kafka integration to handle search request logging and real-time updates.

Guidelines:
- Use FastAPI for creating RESTful API services.
- Utilize PostgreSQL's full-text search features for keyword search.
- Implement synonym search using a suitable library or algorithm.
- Consider scalability and code maintainability.
- Ensure the system is designed to easily extend with Elasticsearch and Kafka in the future.