Best Practices for Configuring MongoDB in .NET

Recently, I had the opportunity to assist in implementing MongoDB in a project, which made me reflect on some essential best practices to ensure an efficient, secure, and scalable configuration within the .NET ecosystem.

MongoDB, with its document-oriented nature, offers flexibility and high performance. However, without proper configuration, challenges related to security, performance, and maintenance can arise. Here are some key points we applied during the implementation:

Proper Connection Management

Managing the database connection correctly is crucial to avoiding overload and ensuring efficient data access. The best approach is to configure the connection once and reuse it throughout the application's lifecycle.

🔹 Example configuration in appsettings.json:

{
  "ConnectionStrings": {
    "MongoConnection": "mongodb://user:password@server:port",
    "DatabaseName": "MyDatabase"
  }
}        

🔹 Configuration in Startup.cs (or Program.cs in .NET 6+):

public void ConfigureServices(IServiceCollection services)
{
    var mongoSettings = Configuration.GetSection("ConnectionStrings");
    var client = new MongoClient(mongoSettings["MongoConnection"]);
    var database = client.GetDatabase(mongoSettings["DatabaseName"]);

    services.AddSingleton<IMongoClient>(client);
    services.AddSingleton(database);
}        

This prevents the unnecessary creation of multiple instances of MongoClient, which is internally managed as a reusable connection.

Proper Indexing

MongoDB allows the creation of indexes to optimize queries, reducing response time and improving performance. Whenever possible, we should define indexes for the most queried fields.

🔹 Example of creating an index in a repository:

public class UserRepository
{
    private readonly IMongoCollection<User> _users;

    public UserRepository(IMongoDatabase database)
    {
        _users = database.GetCollection<User>("Users");

        var indexKeys = Builders<User>.IndexKeys.Ascending(u => u.Email);
        var indexOptions = new CreateIndexOptions { Unique = true };
        var indexModel = new CreateIndexModel<User>(indexKeys, indexOptions);

        _users.Indexes.CreateOne(indexModel);
    }
}        

Here, we ensure that the Email field is unique, preventing duplicate records.

Security: Authentication and Access Control

When configuring MongoDB, especially in production environments, it is essential to apply security best practices, such as authentication and permission restrictions.

🔹 Important Recommendations: ✔ Never expose the connection string in the source code (use environment variables). ✔ Enable authentication and roles in the database, ensuring each service has the minimum required permissions. ✔ Use TLS/SSL to encrypt communication with MongoDB.

Working with DTOs and Models

To avoid information leakage and improve code organization, we use DTOs (Data Transfer Objects) instead of exposing database models directly.

🔹 Example of mapping User to UserDTO:

public class UserDTO
{
    public string Name { get; set; }
    public string Email { get; set; }
}

public class User
{
    public ObjectId Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public string PasswordHash { get; set; } // Do not expose in DTO!
}

public static class UserMapper
{
    public static UserDTO ToDTO(User user)
    {
        return new UserDTO
        {
            Name = user.Name,
            Email = user.Email
        };
    }
}        

This prevents sensitive information, such as passwords, from being returned in public APIs.

Monitoring and Logging

Having visibility into what happens in MongoDB is crucial for identifying bottlenecks and performance issues. We use logging to monitor slow queries and analyze database load.

🔹 Example of enabling logs in .NET:

var settings = new MongoClientSettings
{
    ClusterConfigurator = builder =>
    {
        builder.Subscribe<CommandStartedEvent>(e =>
        {
            Console.WriteLine($"MongoDB Query: {e.CommandName} - {e.Command.ToJson()}");
        });
    }
};

var client = new MongoClient(settings);        

This allows us to capture and analyze queries executed by .NET in MongoDB.

Conclusion

When configuring MongoDB in .NET, the focus should be on connection management, indexing, security, DTOs, and monitoring. The recent experience I had implementing these guidelines in a project was a great learning opportunity, reinforcing the importance of a well-planned setup for scalability and security.

If you have worked with MongoDB in .NET, what challenges have you faced? 🚀 Share your thoughts in the comments!