What is service discovery and how do microservices find each other?

Question

"Service A needs Service B, but B's IP changes on every deploy."

Interview OS Community · Accepted Answer

## Options

**Kubernetes DNS (simplest)**: Services get stable DNS names.
```yaml
kind: Service
metadata: { name: payment-service }
# Other pods call: payment-service:3000
```

**Service Mesh (Istio)**: Sidecar proxy handles routing, retries, load balancing.
```typescript
fetch("http://payment-service/charge"); // Sidecar intercepts → routes → retries
```

| Method | Complexity | Best For |
|--------|-----------|----------|
| DNS (K8s) | Low | Most cases |
| Client registry | Medium | Custom load balancing |
| Service mesh | High | mTLS, observability, complex routing |

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What is service discovery and how do microservices find each other?

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Method	Complexity	Best For
DNS (K8s)	Low	Most cases
Client registry	Medium	Custom load balancing
Service mesh	High	mTLS, observability, complex routing