Integration between Apache Airflow and Hive metastore is facilitated through the Hive Metastore Thrift API, enabling Airflow to interact with Hive for metadata operations and monitoring, ensuring seamless workflow integration.

Built-in functions and User-Defined Functions serve different purposes in Hive. Built-in functions are pre-defined and readily available, while User-Defined Functions are custom functions created by users to fulfill specific requirements. Understanding this difference is crucial for optimizing query performance and extending Hive's functionality.

Integrating Hive with HDFS and YARN requires careful consideration of factors like compatibility with other ecosystem components, data partitioning strategies, high availability setups, and resource allocation optimization to ensure optimal performance and scalability for enterprise-level data processing.

When using User-Defined Functions (UDFs) in Hive queries, various performance considerations must be addressed, including data skew, serialization overhead, resource utilization, and query optimization. Understanding these factors is crucial for optimizing query performance and maintaining efficient cluster operation.

Integrating Hive with YARN enables efficient resource utilization and scalability, as YARN manages and allocates cluster resources dynamically, allowing Hive to handle complex analytical workloads effectively.

Implementing an effective authorization framework in Hive involves considering various access control models such as Role-based access control (RBAC), Attribute-based access control (ABAC), Access control lists (ACLs), and Hierarchical access control (HAC). Each model offers distinct advantages and challenges, and the choice depends on the organization's specific requirements and the complexity of their access control policies.

The Hive-Kafka Integration Plugin enables Hive to subscribe to specific topics in Apache Kafka for real-time data processing, allowing seamless integration between the two systems and enabling real-time analytics and processing of data within Hive queries directly from Kafka topics, enhancing the capabilities of both systems for real-time use cases.

Backup and recovery in distributed Hive environments present challenges such as ensuring data consistency across distributed nodes, managing metadata effectively, and coordinating backup schedules. Overcoming these challenges requires robust strategies and tools to maintain data integrity and reliability across distributed systems, ensuring seamless backup and recovery operations.

Migrating Hive workflows to Apache Airflow involves steps such as assessing and mapping workflows, migrating data, creating DAGs, and performance tuning. Challenges may include compatibility issues, data migration complexities, and performance optimization, which can be mitigated through thorough planning, testing, and optimization strategies.

The Metastore is a crucial component of Hive Architecture responsible for managing and storing all metadata related to Hive tables, schemas, and partitions, enabling efficient query processing and data retrieval.