nosql-expert

Resultado esperado:

For this access pattern, use a composite primary key:

**Partition Key:** user_id (high cardinality - each user is a partition)
**Clustering Column:** order_date DESC (sorts orders by date within each partition)

```sql
CREATE TABLE orders_by_user (
user_id uuid,
order_id uuid,
order_date timestamp,
total decimal,
status text,
PRIMARY KEY (user_id, order_date)
) WITH CLUSTERING ORDER BY (order_date DESC);
```

This design ensures all orders for a user live in one partition (efficient), and they're automatically sorted by date.

Resultado esperado:

**SQL vs Distributed NoSQL Mental Model:**

| Aspect | SQL (Relational) | NoSQL (Cassandra/DynamoDB) |
|-------|------------------|---------------------------|
| Modeling | Model entities + relationships | Model **queries first** |
| Joins | At read time (expensive) | Pre-computed at write time |
| Storage | Minimize duplication | Duplicate for read speed |
| Consistency | ACID (strong) | BASE (eventual) |
| Scaling | Vertical | Horizontal |

**Golden Rule:** In SQL, design data for *any* query. In NoSQL, design data for *specific* queries efficiently.

Resultado esperado:

**DynamoDB Single-Table Design:**

Store multiple entity types in one table using composite keys:

| PK | SK | Data |
|----|-----|------|
| USER#123 | PROFILE | {name: 'Ian', email: '...'} |
| USER#123 | ORDER#998 | {total: 50.00, status: 'shipped'} |
| USER#123 | ORDER#999 | {total: 12.00, status: 'pending'} |

**Query:** PK='USER#123' retrieves user + all orders in ONE request.

**Benefits:**
- Reduced application complexity
- Optimized capacity unit usage
- Single network round-trip for related data