Advanced Systems Architecture Cheat Sheet

The CAP Theorem Reference

• CP (Consistent & Partition Tolerant): Wait for a response from all nodes before confirming a write. (e.g., MongoDB, HBase)
• AP (Available & Partition Tolerant): Return the most recent available version of the data, which might be stale. (e.g., Cassandra, DynamoDB)

Caching Strategies

• Cache-Aside: Application checks cache first. If miss, loads from DB and writes to cache.
• Write-Through: Application writes to cache and DB simultaneously.
• Write-Behind (Write-Back): Application writes to cache, which asynchronously writes to DB.

Disaster Recovery Metrics

• Recovery Time Objective (RTO): The maximum tolerable length of time that a computer, system, network, or application can be down after a failure.
• Recovery Point Objective (RPO): The maximum targeted period in which data (transactions) might be lost from an IT service due to a major incident.