Designing a Database Architecture for Multi-Application Systems: Separate vs Shared Databases

Designing a Database Architecture for Multi-Application Systems

When building applications that share common data but also have unique requirements, it’s essential to consider the best approach for managing their respective databases. In this article, we’ll explore the trade-offs of having separate databases versus sharing a single database among multiple applications.

Understanding Databases as the Unit of Backup and Recovery

Databases are often considered the unit of backup and recovery in software development. This is because databases typically contain all the data required by an application, making them a central point for both data storage and retrieval. When it comes to backups, databases usually involve more complex processes than standalone file systems, requiring tools like SQL backups or even full database dumps.

Understanding Schemas as the Unit for Managing Users and Objects

Schemas are another critical component in database design. A schema defines the structure of a database, including the organization of its data, relationships between tables, and constraints on data values. Schemas are used to manage users and objects within a database. Think of them as containers that hold various types of data together, making it easier for applications to interact with specific data sets.

The Case for Separate Databases

In some cases, having separate databases for each application might be the best choice. Here are some scenarios where this approach makes sense:

Data Isolation: When working with sensitive or confidential information, such as financial data or personal identifiable information (PII), it’s crucial to isolate that data from other applications. Separate databases ensure that each app has its own dedicated space for storing and processing sensitive data.
Scalability: As an application grows in size and complexity, its database requirements can become increasingly demanding. Having separate databases allows you to scale individual applications independently without affecting other apps sharing the same database.
Unique Data Requirements: If two or more applications have significantly different data storage needs (e.g., one app requires a lot of text-based data while another needs extensive image data), having separate databases can help meet those specific requirements.

On the other hand, there are scenarios where sharing a single database among multiple applications makes sense:

Data Sharing: When multiple applications share common data that doesn’t require strict isolation (e.g., product information used across different apps), sharing a single database can simplify data management.
Reduced Complexity: With fewer databases to manage, organizations with multiple applications may experience reduced complexity in terms of database administration and maintenance.

Automatic Data Synchronization

One critical consideration when deciding whether to use separate or shared databases is how you’ll handle data synchronization between apps. In your case, if the shared data needs to update automatically on one app whenever it’s changed in another, having a single database with schema-level permissions can facilitate this process.

Here’s an example of how this might work using PostgreSQL and React/Express applications:

// Assume we have two schemas in our shared database:
-- public_schema
-- private_schema

// Create a function to synchronize data between the schemas
function syncData() {
    // Query the public schema for changes
    const changes = await db.query('SELECT * FROM public_schema WHERE updated_at > NOW() - INTERVAL 1 hour');

    // If there are any changes, update the private schema accordingly
    if (changes.length > 0) {
        changes.forEach((change) => {
            const updatedData = change.data;
            // Perform necessary updates in the private schema
        });
    }
}

PostgreSQL and Schema-Level Permissions

PostgreSQL provides robust support for schema-level permissions, allowing you to control access to specific schemas within your database. This feature is particularly useful when deciding whether to use a shared or separate database.

Here’s an example of how to grant privileges on a particular schema:

-- Create a new user with schema-level permissions
CREATE USER sync_user WITH PASSWORD 'password123';
GRANT SELECT, UPDATE ON public_schema TO sync_user;

React and Express Applications with PostgreSQL

When building progressive web apps (PWAs) using React and Express with PostgreSQL as the database backend, consider how you’ll handle database interactions. Here are some best practices:

Use a library like pg: A popular PostgreSQL driver for Node.js that simplifies connection management.
Implement transactions: To ensure data consistency when performing multiple database operations.

Conclusion

Designing an optimal database architecture depends on the specific requirements of your applications, including data sharing needs and scalability demands. By considering both pros and cons of shared versus separate databases, you can make informed decisions about your database strategy.

Whether you choose to have one or multiple databases, understanding how they’ll interact with your applications is essential for successful software development.

Additional Considerations

Here are a few more considerations when deciding between shared and separate databases:

Data normalization: In some cases, separating data into different schemas can aid in normalization. This helps reduce data redundancy and improve storage efficiency.
Data denormalization: When sharing data across multiple applications, denormalizing the data (i.e., storing redundant information) may be necessary to achieve optimal query performance.

Schema-Level Permissions for PostgreSQL

For organizations with complex database requirements, schema-level permissions can help ensure data security and compliance. Consider how you’ll implement these features in your database architecture.

-- Create a new schema with specific privileges
CREATE SCHEMA public WITH PERMISSIONS (SELECT, UPDATE);

Best Practices for Database Interactions

When building PWAs using React and Express with PostgreSQL as the database backend:

Use transactions: To ensure data consistency when performing multiple database operations.
Implement caching mechanisms: To reduce the load on your database by storing frequently accessed data locally.

By carefully evaluating these factors, you can create an optimal database architecture that meets the unique needs of your applications.

Last modified on 2023-12-26