Services Internal and External communications

Detailed

Excellent question — this is a key topic for SRE and DevSecOps interviews. Let’s break it down clearly and practically:

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🧩 1. Overview: Microservices Communication in EKS

In EKS (Elastic Kubernetes Service), microservices typically run as separate pods and need to communicate securely and reliably. Enterprise setups use a layered architecture for service discovery, traffic routing, security, and observability.

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🏗️ 2. Common Communication Patterns in Enterprises

Type	Description	Common Tools/Components
Service-to-Service (East–West traffic)	Internal communication between microservices (e.g., orders → payments)	- Kubernetes DNS (ClusterIP Services)- Istio / Linkerd (Service Mesh)- mTLS for encryption
Ingress (North–South traffic)	External traffic coming from the internet into the cluster	- AWS ALB / NLB- Ingress Controller (Nginx, Istio Gateway, Kong, Traefik)- WAF or API Gateway (AWS API Gateway / Kong / Apigee)
Egress	Outbound traffic from the cluster to external APIs or databases	- Istio Egress Gateway- NAT Gateway or VPC Endpoints- NetworkPolicies for control
Async / Event-driven	Decoupled communication for background jobs or events	- Kafka / RabbitMQ / SQS / SNS- EventBridge- Redis Streams

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🧱 3. Common Enterprise EKS Communication Architecture (Mid-Level Setup)

Here’s what you’d typically see:

                ┌───────────────────────────────┐
                │       External Users          │
                └────────────┬──────────────────┘
                             │
                      ┌──────▼──────┐
                      │ AWS ALB/NLB │   ← (Ingress)
                      └──────┬──────┘
                             │
                ┌────────────▼────────────┐
                │ Ingress Controller (e.g.│
                │ Nginx / Istio Gateway)  │
                └────────────┬────────────┘
                             │
                  ┌──────────▼───────────┐
                  │  Service Mesh (Istio │
                  │  / Linkerd Sidecars) │
                  └──────────┬───────────┘
                             │
              ┌──────────────┼──────────────┐
              │              │              │
        ┌─────▼────┐   ┌────▼────┐   ┌────▼────┐
        │ orders   │   │ payment │   │ users   │   ← (Microservices)
        └─────┬────┘   └────┬────┘   └────┬────┘
              │             │             │
              │   (mTLS, L7 routing,      │
              │    retries, tracing)      │
              │             │             │
          ┌───▼───────────────────────────▼───┐
          │   Internal Databases / Message Bus │
          │   (RDS / DynamoDB / Kafka / Redis) │
          └────────────────────────────────────┘

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🔐 4. Security & Access Control

Layer	Security Mechanism
Network	AWS VPC, private subnets, Security Groups
Pod-to-Pod	NetworkPolicy, Istio mTLS, Authz Policies
API Layer	JWT/OAuth2, API Gateway authentication
Secrets	AWS Secrets Manager / KMS, sealed-secrets

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📊 5. Observability Stack (Typical Enterprise Setup)

Function	Tools
Metrics	Prometheus + Grafana
Tracing	Jaeger / Tempo / X-Ray
Logging	EFK (Elasticsearch + Fluentbit + Kibana) or CloudWatch
Alerts	Alertmanager / PagerDuty / Opsgenie

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🧠 6. Example Communication Flow

Let’s say a user places an order:

1. User → ALB → Ingress Controller → orders-service

2. orders-service calls payment-service via Service Mesh (Istio handles retries, timeout, and mTLS)

3. payment-service publishes an event to Kafka/SQS

4. notification-service consumes the event and sends an email

5. Traces and metrics go to Prometheus + Grafana + Jaeger

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⚙️ 7. Common Tools Stack for Mid-Level Enterprises

Layer	Common Tools
Kubernetes Platform	EKS (managed control plane)
Networking / Ingress	AWS ALB + Nginx / Istio Gateway
Service Mesh	Istio / Linkerd
API Gateway (Optional)	AWS API Gateway / Kong
Messaging	Kafka / RabbitMQ / SQS
Observability	Prometheus, Grafana, Jaeger
Security	IAM, IRSA, KMS, mTLS, NetworkPolicies

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Would you like me to diagram this as a visual architecture (image) — showing how microservices, Istio, Ingress, and observability components connect inside EKS? It’ll help you explain easily in interviews.