Message Delivery Isn't Business Execution

One production lesson I learned the hard way over the last 3+ years:

Never mix message delivery reliability with job execution reliability.

A message arriving successfully does not mean the work was completed successfully.

A message broker's responsibility is communication, not execution.

Once you separate event delivery from business execution, you gain independent control over retries, concurrency, and failure handling.

Different responsibilities.

Different guarantees.

More resilient systems.