Choosing Your Database Weapon

The Database Decision Tree:

Start here: What does your application actually DO with data?

Scenario 1: Simple Lookups

• "Get user profile by ID"
• "Fetch order by order number"
• "Retrieve session by token"

→ Choose: Key-Value Store (Redis, DynamoDB)

• Lightning fast
• Scales horizontally like crazy
• Simple to understand and maintain

Scenario 2: Flexible Data + Complex Queries

• "Show me all notifications from last week"
• "Find products in category X under $50"
• "Aggregate user activity data"

→ Choose: Document Database (MongoDB, Elasticsearch)

• JSON-like flexibility
• SQL-like query power
• Great for evolving schemas

Scenario 3: Relationship-Heavy Operations

• "Find shortest path between users"
• "Detect fraud patterns across transactions"
• "Build recommendation engines"

→ Choose: Graph Database (Neo4j, Neptune)

• Built-in graph algorithms
• Optimized for traversals
• Perfect for network analysis

Scenario 4: Strong Consistency + Complex Transactions

• "Banking transactions"
• "Inventory management"
• "Multi-step workflows"

→ Choose: Relational Database (PostgreSQL, MySQL)

• ACID guarantees
• Mature ecosystem
• Well-understood patterns

Key Insight: "The best database isn't the fanciest one - it's the one that matches your access patterns and scaling needs."