Custom Serdes are essential for integrating Hive with Kafka, as they enable the conversion of data formats between Kafka topics and Hive tables, ensuring seamless data transfer and compatibility between the two systems, crucial for real-time analytics and data processing pipelines.

Using Tez or Spark as execution engines for Hive queries provides notable advantages, especially in terms of improved query performance. These engines leverage in-memory processing and advanced execution optimizations, which result in faster query execution times compared to the traditional MapReduce engine, making them highly suitable for complex and large-scale Hive queries within the Hadoop ecosystem.

To ensure high availability and fault tolerance in a Hive setup, focusing on components like HDFS and ZooKeeper is crucial. HDFS replicates data across nodes, ensuring availability, while ZooKeeper manages configurations and maintains the availability of services like NameNode and Hive metastore. These components form the backbone of fault tolerance and high availability in a Hive deployment, laying the foundation for a robust analytics infrastructure.

Configuring Hive for multi-node cluster deployment, implementing ZooKeeper for cluster coordination, enabling Hive replication for data redundancy, and setting up automatic failover for Hive components are essential steps during Hive installation to achieve high availability and fault tolerance, ensuring uninterrupted operations and resilience against failures in the enterprise environment.

When integrating Hive with Apache Druid, the data ingestion process can involve various methods such as Direct Ingestion, Batch Ingestion, Real-time Ingestion, and Incremental Ingestion. Each method has its own advantages and use cases, providing flexibility in managing data ingestion based on requirements and constraints.

A comprehensive security strategy for Hive involves implementing network segmentation to isolate clusters, conducting regular security assessments and penetration testing, encrypting sensitive data, and hardening Hive configurations with prompt security patching. These measures help mitigate security vulnerabilities and data breaches, aligning with industry best practices to ensure robust security for the financial institution's data warehouse solution.

Scaling up a Hive cluster requires careful consideration of factors such as horizontal scaling, dynamic resource allocation, partitioning and bucketing techniques, and auto-scaling policies. By expanding the cluster horizontally, implementing dynamic resource allocation, optimizing data organization, and configuring auto-scaling policies, enterprises can ensure efficient resource utilization and minimal performance degradation, effectively meeting growing data processing demands with scalability and elasticity.

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.