3. When to use NoSQL?

Choosing between SQL (relational) and NoSQL databases depends on the requirements of the application. NoSQL databases are ideal for specific scenarios where flexibility, scalability, and performance are critical.

Key Use Cases for NoSQL

1. Applications with Rapidly Changing Requirements

• NoSQL databases provide a flexible schema, allowing you to add or modify fields without downtime.
• Suitable for agile development environments or when the application evolves frequently.
• Example:
  • A startup launching a new social media app can quickly adapt to changing user demands by modifying data models without worrying about rigid schema constraints.

2. Big Data and High-Volume Applications

• Designed to handle large-scale, unstructured, or semi-structured data.
• Optimized for distributed storage and processing across multiple servers.
• Example:
  • An IoT application collecting sensor data from millions of devices benefits from NoSQL’s ability to scale horizontally and store diverse data formats.

3. Real-Time Applications

• NoSQL databases are optimized for low-latency reads and writes, enabling real-time performance.
• Common in use cases like gaming, financial transactions, or social media feeds.
• Example:
  • A gaming platform with real-time leaderboards and player statistics requires fast reads/writes to keep users engaged.

4. Hierarchical or Nested Data

• NoSQL’s document-oriented databases, like MongoDB, are well-suited for representing hierarchical data structures.
• No need for complex joins as in relational databases.
• Example:
  • An e-commerce application can represent products, reviews, and user data in nested JSON documents, making querying simpler and faster.

5. Scalability and High Availability

• Applications expecting exponential growth in users or data benefit from NoSQL’s horizontal scalability.
• Sharding and replication ensure high availability and fault tolerance.
• Example:
  • A global streaming service can distribute data geographically, ensuring users in different regions experience low latency.

Specific Situations Where NoSQL Excels

1. Content Management Systems (CMS)

• Flexible schema accommodates diverse content types like articles, videos, and images.
• NoSQL can efficiently store metadata and relationships between content items.

2. Event Logging and Analytics

• Handles high write loads for logging user activity or system events.
• NoSQL’s schema flexibility supports various log formats.
• Example:
  • A web analytics platform tracking user clicks and page views in real-time benefits from NoSQL’s ability to store and process large volumes of unstructured data.

When Not to Use NoSQL

• While NoSQL is powerful, there are scenarios where it may not be the best fit:

1. Complex Transactions

• Relational databases excel at multi-step transactions requiring strict ACID compliance.
• NoSQL databases, while improving in this area, may not guarantee the same level of consistency.

2. Strongly-Structured Data

• If your application involves fixed schemas with well-defined relationships, SQL databases may be more appropriate.
• Example: A financial system requiring rigid data integrity and complex joins.

3. Limited Querying Needs

• NoSQL’s rich querying capabilities might be unnecessary for simple, low-volume applications.

Key Considerations Before Choosing NoSQL

1. Data Structure Flexibility:
   • Are your data schemas likely to evolve over time?
2. Scalability Needs:
   • Do you anticipate large data volumes or high user traffic?
3. Application Requirements:
   • Does your app prioritize low-latency operations or complex relational queries?
4. Budget and Infrastructure:
   • Can you manage the complexities of distributed systems if horizontal scaling is required?