In which reply is it possible to read large volumes of data?

Reading large volumes of data in Go usually occurs on a replica configured as a read replica (read-only replica). This allows offloading the primary database (master) and increasing performance when executing heavy read queries.

For example, in architectures with PostgreSQL or MySQL databases, the primary replica (master) handles both read and write operations, while additional replicas are only for reading. In Go code, read requests can be directed specifically to the read replica to efficiently handle large data volumes.

An example of using a read replica in Go with the database/sql library and custom query routing:

// dbMaster - connection to the master
// dbReplica - connection to the replica

func queryLargeData(readOnly bool) ([]Data, error) {
    var db *sql.DB
    if readOnly {
        db = dbReplica
    } else {
        db = dbMaster
    }
    rows, err := db.Query("SELECT * FROM large_table")
    if err != nil {
        return nil, err
    }
    defer rows.Close()

    var results []Data
    for rows.Next() {
        var d Data
        if err := rows.Scan(&d.Field1, &d.Field2); err != nil {
            return nil, err
}
        results = append(results, d)
    }
    return results, nil
}

Thus, large data volumes are read from the replica, reducing the load on the primary database.