nosql-expert

version	4.1.0-fractal
name	nosql-expert
description	Expert guidance for distributed NoSQL databases (Cassandra, DynamoDB). Focuses on mental models, query-first modeling, single-table design, and avoiding hot partitions in high-scale systems.

NoSQL Expert Patterns (Cassandra & DynamoDB)

Overview

This skill provides professional mental models and design patterns for distributed wide-column and key-value stores (specifically Apache Cassandra and Amazon DynamoDB).

Unlike SQL (where you model data entities), or document stores (like MongoDB), these distributed systems require you to model your queries first.

When to Use

• Designing for Scale: Moving beyond simple single-node databases to distributed clusters.
• Technology Selection: Evaluating or using Cassandra, ScyllaDB, or DynamoDB.
• Performance Tuning: Troubleshooting "hot partitions" or high latency in existing NoSQL systems.
• Microservices: Implementing "database-per-service" patterns where highly optimized reads are required.

The Mental Shift: SQL vs. Distributed NoSQL

Feature	SQL (Relational)	Distributed NoSQL (Cassandra/DynamoDB)
Data modeling	Model Entities + Relationships	Model Queries (Access Patterns)
Joins	CPU-intensive, at read time	Pre-computed (Denormalized) at write time
Storage cost	Expensive (minimize duplication)	Cheap (duplicate data for read speed)
Consistency	ACID (Strong)	BASE (Eventual) / Tunable
Scalability	Vertical (Bigger machine)	Horizontal (More nodes/shards)

The Golden Rule: In SQL, you design the data model to answer any query. In NoSQL, you design the data model to answer specific queries efficiently.

Core Design Patterns

🧠 Knowledge Modules (Fractal Skills)

1. 1. Query-First Modeling (Access Patterns)

2. 2. The Partition Key is King

3. 3. Clustering / Sort Keys

4. 4. Single-Table Design (Adjacency Lists)

5. 5. Denormalization & Duplication

6. Apache Cassandra / ScyllaDB

7. AWS DynamoDB