MQTT vs Kafka — both are messaging systems, but they’re designed for very different use cases. Here’s a breakdown to help clarify when to use which:

⚡ Quick Comparison:

Feature MQTT Apache Kafka
Protocol Type Lightweight messaging protocol Distributed streaming platform
Designed For IoT devices, constrained networks High-throughput, large-scale data pipelines
Message Model Pub/Sub Pub/Sub + log-based storage
Persistence Optional, often not used Built-in, durable, distributed log
QoS Levels 0 (at most once), 1 (at least once), 2 (exactly once) At least once (default), exactly once (configurable)
Broker Complexity Lightweight (e.g., Mosquitto) Heavy (e.g., Kafka needs Zookeeper or KRaft)
Latency Low Low to medium, optimized for throughput
Storage Minimal to none Retains messages (configurable retention)
Scalability Limited (single broker common) Highly scalable and distributed
Security TLS, username/password TLS, SASL, ACLs, etc.
Typical Use Cases IoT sensors, mobile devices, telemetry Event sourcing, log aggregation, analytics pipelines

🧠 TL;DR:

  • Use MQTT when:
    • You have resource-constrained devices (IoT, edge computing).
    • You need real-time messaging over unstable or low-bandwidth networks.
    • You care about lightweight, battery-friendly communication.
    • Example: Smart thermostats sending temperature data every few seconds.
  • Use Kafka when:
    • You need to handle millions of events per second.
    • You want to persist messages for replay, analytics, or audit trails.
    • You’re building complex data pipelines or event-driven systems.
    • Example: Website clickstream analysis, financial transaction processing.