Columnar databases store data by columns, offering faster query performance and efficiency in large-scale analytics and data warehousing. They are optimized for read-heavy operations like aggregations and filtering, reducing I/O operations and improving storage costs. Columnar databases are ideal for analytical queries, business intelligence, data warehousing, big data processing, log and event data analysis, and machine learning workloads. Examples of columnar databases include Capella Columnar, Amazon Redshift, Google BigQuery, Apache Parquet, and ClickHouse. However, they may not be suitable for high-frequency transactional workloads, small-scale applications, frequent row-level operations, real-time, low-latency writes, or traditional relational database use cases. Modern data architectures often combine columnar and relational databases to address different needs within the same application or organization, leveraging their complementary capabilities.