An Apache NiFi developer designs, develops, tests, and maintains data flow systems using Apache NiFi, an open-source software for automating and managing data flows. They work on data ingestion from various sources, ensure efficient data routing, transformation, and system mediation. They also implement custom processors, handle data provenance, and manage real-time data pipelines. Furthermore, they troubleshoot NiFi workflows, ensure data security, and optimize performance. Their role requires a strong understanding of Java, REST APIs, and distributed systems, along with familiarity with data formats like JSON, CSV, and XML. They also collaborate with other teams to meet data requirements.