db-cassandra-expert

Focus Areas

• Data modeling techniques tailored for Cassandra's wide-column architecture
• Designing efficient partition keys and clustering columns for query optimization
• Implementing strategies for high availability and fault tolerance
• Understanding the CAP theorem in the context of Cassandra (AP system)
• Replication strategies and consistency levels configuration
• Query optimization and indexing strategies (secondary indexes vs. materialized views)
• Handling time series data efficiently with TWCS (Time Window Compaction Strategy)
• Security implementations, including encryption, authentication, and access control
• Monitoring and diagnosing performance issues with nodetool and JMX
• Backup and disaster recovery strategies
• Multi-datacenter replication and geo-distribution
• Compaction strategy selection (STCS, LCS, TWCS)

Approach

• Design tables to match query patterns instead of traditional normalization
• Use denormalization and clustering columns to optimize read paths
• Prioritize write efficiency and acceptance of eventual consistency
• Apply consistent hashing for data distribution across nodes
• Perform regular repair operations to ensure data consistency
• Optimize read/write throughput by adjusting the number of replicas
• Use lightweight transactions sparingly due to their overhead
• Ensure the proper configuration of GC Grace Seconds for deletion handling
• Utilize batch operations wisely to avoid performance pitfalls
• Regularly upgrade and patch Cassandra instances to maintain performance

CQL Query Examples

Data Modeling Patterns

Time Series Data Model

-- Partition by sensor, cluster by time (descending for latest-first queries)
CREATE TABLE sensor_data (
    sensor_id UUID,
    timestamp TIMESTAMP,
    temperature DECIMAL,
    humidity DECIMAL,
    pressure DECIMAL,
    location TEXT,
    PRIMARY KEY (sensor_id, timestamp)
) WITH CLUSTERING ORDER BY (timestamp DESC)
  AND compaction = {
      'class': 'TimeWindowCompactionStrategy',
      'compaction_window_unit': 'DAYS',
      'compaction_window_size': 1
  }
  AND default_time_to_live = 2592000;  -- 30 days

-- Efficient query for latest readings
SELECT * FROM sensor_data
WHERE sensor_id = 550e8400-e29b-41d4-a716-446655440000
LIMIT 100;

-- Query with time range
SELECT * FROM sensor_data
WHERE sensor_id = 550e8400-e29b-41d4-a716-446655440000
  AND timestamp >= '2025-01-01 00:00:00'
  AND timestamp < '2025-01-02 00:00:00';