streaming-and-messaging-systems

Streaming And Messaging Systems

Overview

Use this skill for continuous data movement and real-time processing. It helps agents design safe event pipelines around brokers and stream processors such as Kafka, Kinesis, and Flink, with attention to ordering, state, replay, schema evolution, and delivery guarantees.

When to Use

• designing or modifying Kafka topics, consumers, or stream processors
• using Kinesis for event ingestion or streaming delivery
• implementing Flink jobs or stateful stream transformations
• defining near-real-time pipelines, windows, watermarks, and replay behavior
• handling schemas and contracts for event-driven systems

Do not use this when the workload is purely batch and does not require streaming semantics.

Workflow

1. Define the event contract. Include:

   • event key
   • schema and versioning
   • ordering expectations
   • delivery guarantees
   • retention and replay policy

2. Choose the right platform role.

   • Kafka: durable event backbone and broad ecosystem
   • Kinesis: AWS-native streaming ingestion and transport
   • Flink: stateful stream processing and event-time logic

3. Design for state and late data. Account for:

   • watermarks
   • windows
   • deduplication
   • exactly-once or at-least-once semantics
   • checkpointing and recovery

4. Make consumer behavior observable. Lag, failed checkpoints, poison messages, schema drift, and dead-letter handling should be planned, not discovered in production. For production Kafka hardening, load kafka-resilience-and-schema-evolution. For live lag or broker metadata before changes, load mcp-data-observability-integration.

5. Treat replay as a first-class operation. Reprocessing events should not depend on manual guesswork.

Common Rationalizations

Rationalization	Reality
"Streaming just means faster batch."	Streaming introduces ordering, state, replay, and time semantics that batch systems do not have.
"We can ignore schema evolution because events are small."	Event size does not reduce contract risk; schema drift can break many downstream consumers.
"Exactly-once is automatic."	Delivery semantics depend on end-to-end design, state handling, sinks, and replay behavior.

Red Flags

• no explicit event contract or key strategy
• replay and retention are undefined
• time semantics are assumed instead of specified
• consumer lag and dead-letter strategy are missing
• stateful processing has no checkpoint or recovery plan

Verification

• Event schema, keys, retention, and replay rules are defined
• Platform responsibilities are clear across broker and processor layers
• Time semantics, state, and recovery design are explicit
• Operational visibility exists for lag, failures, and bad records