Let’s revise what were the responsibilities of Enterprise Service Buses:

• service discovery and communication
• request routing
• protocol mediation
• authN and authZ
• rate limiting
• logging and monitoring
• workflow orchestration

These capabilities are generic. Any sufficiently complex system needs them — but they don’t need to live inside a single, centralized component.

In cloud-native systems, ESBs were effectively decomposed into specialized services:

• service discovery -> service mesh tools (AppMesh, Linkerd)
• service communication -> messaging and event streaming platforms (Kafka, SQS)
• request routing, rate limiting, auth -> API gateways
• logging and monitoring -> observability tools (CloudWatch, CloudTrail)
• orchestration -> workflow engines (Step Functions)

What remained were microservices themselves:

• independently developed
• independently deployed
• independently scaled
  ...units of a system, focused on isolated business capabilities.