While decoupling sounds great in theory, it often introduces invisible coupling – dependencies on event contracts, formats, topics, and message semantics.

Here is where things get messy:

• Versioning Hell: Changing the shape of an event becomes a breaking change. You can’t just refactor like you do with REST APIs protected by versioned routers.
• Debugging is a Nightmare: Tracing a single business flow across multiple event consumers is like playing detective with a half-burned trail.
• Testing Becomes Harder: You can’t simply hit an endpoint and check the response. You are to simulate events, mock broken, and guess what’s broken.
• Operational Overhead: Kafka clusters are not trivial to operate. You’ll need Zookeeper (or Kraft), manage partitions, monitor offsets, and deal with worker crashing.

What was meant to simplify scalability ends up complicating development and operations – especially for small and mid-sized teams.