Have you had experience working with the Transactional Outbox mechanism to ensure reliable message delivery?

Yes, the Transactional Outbox mechanism is used to ensure reliable message delivery between services in distributed systems.

The essence of the mechanism:

• Instead of sending a message directly at the moment of business logic processing, the message is stored in a special table (outbox) within the same transaction as the main database operation.
• After the transaction commits successfully, a separate process or service reads messages from the outbox and sends them to a queue or another recipient.

This guarantees that the message will not be lost, even if the sending process is interrupted, and eliminates the problem of desynchronization between the database state and the messaging system.

An example in C# using Entity Framework might look like this:

using(var transaction = context.Database.BeginTransaction())
{
    // Main operation
    context.Orders.Add(newOrder);

    // Add message to outbox
    context.OutboxMessages.Add(new OutboxMessage { Payload = serializedMessage });

    context.SaveChanges();
    transaction.Commit();
}

// A separate process reads from OutboxMessages and sends messages