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Explanation

Yes, we can use two (or more) databases in the same project. This is called multi-database configuration. It allows an application to connect and interact with multiple data sources simultaneously.

Code:

@ConfigurationProperties(prefix = 
"spring.datasource.db1")
    public DataSource dataSource1() {
        return DataSourceBuilder.create().
build();
    }

    @ConfigurationProperties(prefix = 
"spring.datasource.db2")
    public DataSource dataSource2() {
        return DataSourceBuilder.create()
.build();
    }

Explanation

Why needed: To separate concerns such as storing user data in one database and logs or analytics in another. This improves performance and maintainability.

Code:

// Example usage
// DB1 -> User data
// DB2 -> Logs data

Explanation

It is useful when integrating legacy systems where data already exists in different databases and needs to be accessed in a single application.

Code:

// Example: Old system DB + 
New system DB used together

Explanation

Multi-database setup helps in scaling applications by distributing load across databases, such as read/write separation (one DB for writes, another for reads).

Code:

// Example
// Master DB -> write operations
// Replica DB -> read operations

Explanation

Real-time usage: Used in microservices, large enterprise systems, and applications requiring high availability, data isolation, or different database technologies (e.g., MySQL + MongoDB).

Code:

// Example
// MySQL -> transactional data
// MongoDB -> unstructured data