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Cassandra AWS System Memory Guidelines 2025: Optimizing for Modern Hardware and Workloads

System Memory Guidelines for Cassandra AWS - 2025 Edition

What’s New in 2025

The Cassandra memory landscape has evolved significantly:

1. Modern JVMs - Java 21 LTS with ZGC and Shenandoah GC offer sub-millisecond pause times
2. AWS Graviton3 - ARM-based processors with DDR5 memory provide 50% better memory bandwidth
3. Larger heap sizes - Modern GCs handle 100GB+ heaps efficiently
4. Container deployments - Memory management in Kubernetes requires different approaches
5. Persistent memory - Intel Optane and similar technologies blur the line between RAM and storage
6. Tiered storage - Hot data in memory, warm in NVMe, cold in S3
7. Vector search workloads - New memory requirements for AI/ML applications

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Cassandra AWS System Memory Guidelines

System Memory Guidelines for Cassandra AWS

Basic guidelines for AWS Cassandra

Do not use less than 8GB of memory for the JVM. The more RAM the better. Use G1GC. SSTable are first stored in memory and then written to disk sequentially. The larger the SSTable the less scanning that needs to be done while reading and determining if a key is in an SSTable using a bloom filter. In the EC2 world this equates to an m4.xlarge (16GB of memory), and you need some memory for the OS, specifically the IO buffers. The i2.xlarge and d2.xlarge are the smallest in their family and exceed the min memory requirement (and then some).

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