Zero Trust for Microservices: Security Patterns That Hold Up

In a microservices system, hundreds of services talk to each other all day. The old idea of a trusted internal network no longer holds: once an attacker is inside, flat networks let them move freely.

Zero trust flips the default. Nothing is trusted because of where it sits on the network. Every request is authenticated, authorised and checked.

Secure service-to-service traffic

A service mesh such as Istio or Cilium can encrypt traffic between services with mutual TLS and enforce authorisation policies, usually without changes to application code.

• Give every workload its own identity
• Encrypt all internal traffic by default
• Write explicit allow rules for which service may call which

Treat the API gateway as a checkpoint

The gateway is the first line of defence for external traffic. Use it for authentication, rate limiting, request validation and bot protection, but do not assume that traffic is safe just because it passed through.

Keep data access narrow

Each service should own its data and expose it only through its API. Sharing one database across services creates hidden coupling and a large blast radius.

• Encrypt data in transit and at rest
• Give each service its own least-privilege database credentials
• Log and review access to sensitive data

Design for compromise

Assume that any single service can be breached. Limit what it can reach, rotate its credentials automatically, and monitor for unusual behaviour so that one failure stays small.