Using Amazon Aurora MySQL for Applications That Still Need MySQL Compatibility

The cluster endpoint should be used for write operations such as INSERT, UPDATE, and DELETE.

It can also handle read queries.

The reader endpoint is designed for read-only workloads such as reporting, dashboards, and data retrieval.

One important detail is that the reader endpoint balances connections, not individual SQL queries. If an application keeps one connection open, its queries continue using the instance selected for that connection.

This distinction matters when implementing connection pooling.

Implement Database Access Using C#

Let's create a simple repository that retrieves customer information from Aurora.

The example uses the MySqlConnector library directly.

using MySqlConnector;

public class CustomerRepository
{
    private readonly string _connectionString;

    public CustomerRepository(IConfiguration configuration)
    {
        _connectionString =
            configuration.GetConnectionString("AuroraWriter")
            ?? throw new InvalidOperationException(
                "Aurora connection string is missing.");
    }

    public async Task<Customer?> GetCustomerAsync(
        int customerId,
        CancellationToken cancellationToken)
    {
        await using var connection =
            new MySqlConnection(_connectionString);

        await connection.OpenAsync(cancellationToken);

        const string sql = """
            SELECT CustomerId, CustomerName, Email
            FROM Customers
            WHERE CustomerId = @CustomerId;
            """;

        await using var command =
            new MySqlCommand(sql, connection);

        command.Parameters.AddWithValue(
            "@CustomerId",
            customerId);

        await using var reader =
            await command.ExecuteReaderAsync(cancellationToken);

        if (!await reader.ReadAsync(cancellationToken))
        {
            return null;
        }

        return new Customer
        {
            CustomerId = reader.GetInt32("CustomerId"),
            CustomerName = reader.GetString("CustomerName"),
            Email = reader.GetString("Email")
        };
    }
}

public class Customer
{
    public int CustomerId { get; set; }

    public string CustomerName { get; set; } = string.Empty;

    public string Email { get; set; } = string.Empty;
}

The important part is that the repository uses a standard MySQL connection.

There is no special Aurora-specific SQL syntax in this example.

The application opens a connection, executes a parameterized query, and reads the result.

This is one of the reasons Aurora can be attractive for applications that already use MySQL.

However, always test your existing SQL queries, stored procedures, triggers, and database features against the selected Aurora engine version before migration.

Separate Read and Write Operations

As an application grows, sending every query to the primary database instance can increase its workload.

Aurora allows developers to distribute read-only operations across Aurora Replicas.

A practical approach is to maintain separate connection strings.

For example:

public class CustomerReadRepository
{
    private readonly string _connectionString;

    public CustomerReadRepository(IConfiguration configuration)
    {
        _connectionString =
            configuration.GetConnectionString("AuroraReader")
            ?? throw new InvalidOperationException(
                "Aurora reader connection string is missing.");
    }
}

Use the writer endpoint for operations that modify data and the reader endpoint for suitable read-only operations.

However, do not send every SELECT query to a reader automatically.

Consider an application that creates an order and immediately retrieves it.

If the read goes to a reader before replication has made the latest changes visible, the application may temporarily return stale information.

For read-after-write scenarios that require immediate consistency, use the writer endpoint.

For reporting and other workloads that can tolerate replication lag, the reader endpoint is generally more appropriate.

Plan for Automatic Failover

Database availability is an important consideration for production applications.

Aurora automatically detects failures of the primary instance and can promote an available Aurora Replica to become the new primary.

The cluster endpoint automatically follows the new primary instance.

This means applications do not need to permanently store the hostname of a particular writer instance.

However, automatic failover does not mean existing application connections will never fail.

During failover, active connections can be interrupted. Applications should be prepared to reconnect and retry appropriate operations.

For .NET applications, consider the following practices:

• Use the Aurora cluster endpoint instead of a fixed instance endpoint for writes.
• Configure sensible connection timeouts.
• Handle transient database errors.
• Reopen connections when necessary.
• Use bounded retries with appropriate backoff.
• Avoid retrying non-idempotent operations without checking whether the previous operation succeeded.
• Test failover behavior before production deployment.

For applications requiring additional connection management, Amazon RDS Proxy can also be evaluated.

Understand the Limitations of MySQL Compatibility

Although Aurora supports MySQL compatibility, developers should not assume that every MySQL feature is available.

Some features and behaviors differ because Aurora uses its own database architecture and managed implementation.

Before migration, review:

• Storage engine requirements.
• Stored procedures and triggers.
• Replication and binary logging requirements.
• User authentication plugins.
• Database parameter settings.
• SQL modes and server variables.
• Third-party extensions and integrations.
• Administrative privileges and unsupported operations.

For example, applications that depend on a particular MySQL storage engine or low-level server configuration may require changes.

Aurora MySQL 8.4 also introduces security-related differences. New clusters enforce TLS by default, and new accounts use the caching_sha2_password authentication plugin.

Applications with older database drivers or authentication configurations should be tested before upgrading.

Do not treat a successful database connection as proof that the entire application is compatible.

Summary

Amazon Aurora MySQL provides a managed database option for applications that need to retain their existing MySQL ecosystem.

Its compatibility allows many applications to reuse existing SQL queries, drivers, and database access code. At the same time, Aurora introduces a distributed storage architecture, managed backups, read replicas, and automatic failover.

For .NET applications, MySqlConnector provides a familiar way to connect to Aurora using standard ADO.NET patterns.

The most important implementation decisions involve selecting the correct MySQL-compatible engine version, using the appropriate database endpoints, separating read and write workloads, and preparing the application for connection interruptions during failover.

Aurora can reduce database infrastructure management, but compatibility should always be verified against the application's actual SQL, drivers, authentication requirements, and operational workload before moving production data.