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Kubernetes API Request Flow Architecture

Table of Contents

Overview

This document outlines the comprehensive journey of an API request in a production Kubernetes environment, from the initial client request to response delivery. The architecture follows industry best practices for security, performance, and reliability, implementing a multi-layered approach to protect and efficiently deliver API services.

The document details how requests flow through each architectural component, focusing on security aspects, performance considerations, and potential failure points. It provides infrastructure teams and technical architects with an in-depth understanding of the platform's request handling mechanisms.

Architecture Components

The key components in our Kubernetes API request flow architecture include:

  1. Client Application: The source of API requests (mobile app, web application, or third-party service)
  2. Akamai CDN/Edge Protection: Global content delivery network and edge protection layer
  3. NGINX Ingress Controller: Kubernetes entry point for external HTTP/HTTPS traffic
  4. Kubernetes Ingress Resources: Kubernetes objects defining routing rules
  5. Kubernetes Services: Internal load balancing and service discovery mechanism
  6. Kubernetes Pods: Running application containers that process requests
  7. Service Backends: Databases, caches, and other backing services

Request Flow Sequence Diagram

sequenceDiagram
    participant Client
    participant Akamai as Akamai CDN/Edge
    participant NGINX as NGINX Ingress Controller
    participant KIngress as Kubernetes Ingress
    participant KService as Kubernetes Service
    participant Pod as Application Pod
    participant Backend as Backend Services

    Note over Client,Backend: Request Flow

    Client->>Akamai: HTTPS Request
    Note right of Akamai: TLS Termination<br/>WAF Processing<br/>DDoS Protection<br/>Edge Caching Check

    alt Cached Response Available
        Akamai-->>Client: Return Cached Response
    else Cache Miss
        Akamai->>NGINX: Re-encrypted HTTPS Request
        Note right of NGINX: TLS Termination<br/>Request Routing<br/>Rate Limiting

        NGINX->>KIngress: HTTP Request
        Note right of KIngress: Routing Rule<br/>Application

        KIngress->>KService: Routed Request
        Note right of KService: Load Balancing<br/>Service Discovery

        KService->>Pod: Request to Selected Pod
        Note right of Pod: Request Processing<br/>Business Logic<br/>Authentication

        alt External Data Required
            Pod->>Backend: Backend Service Request
            Backend-->>Pod: Backend Response
        end

        Pod-->>KService: Response
        KService-->>KIngress: Response
        KIngress-->>NGINX: Response

        Note right of NGINX: Response<br/>Processing<br/>Compression

        NGINX-->>Akamai: HTTPS Response

        Note right of Akamai: Response Caching<br/>Edge Optimization

        Akamai-->>Client: HTTPS Response
    end

    Note over Client,Backend: Response Flow Complete
System Diagram

Component Roles and Responsibilities

Client Application

  • Role: Originates API requests to the platform
  • Responsibilities:
  • Forms properly structured API requests
  • Handles authentication tokens/credentials
  • Processes responses
  • Implements retry logic and circuit breaking
  • Maintains secure TLS connections

Akamai CDN/Edge Protection

  • Role: Provides edge protection, global distribution, and performance optimization
  • Responsibilities:
  • DDoS Mitigation: Protection against volumetric and application-layer attacks
  • Web Application Firewall (WAF): Blocks common exploitation techniques and attacks
  • TLS Termination: Handles initial client SSL/TLS connections
  • Content Caching: Stores and serves cacheable API responses
  • Request Filtering: Blocks malicious traffic based on signatures and behavior
  • Geographic Distribution: Routes requests to nearest data centers
  • Rate Limiting: Enforces global rate limits to protect backend services
  • Bot Detection: Identifies and manages automated traffic
  • Edge Computing: May execute simple transformations at the edge

NGINX Ingress Controller

  • Role: Acts as the entry point for external traffic into the Kubernetes cluster
  • Responsibilities:
  • TLS Termination: Handles HTTPS connections from Akamai
  • Request Routing: Directs traffic to appropriate services based on URL paths
  • Load Balancing: Distributes traffic across multiple service instances
  • Rate Limiting: Provides service-specific rate controls
  • SSL/TLS Management: Manages certificates for secure communication
  • Request/Response Manipulation: Modifies headers, performs redirects
  • Authentication: Optional integration with auth services
  • Health Checks: Monitors backend services
  • Metrics Collection: Captures detailed request metrics

Kubernetes Ingress Resources

  • Role: Declarative definition of how external HTTP traffic should be routed
  • Responsibilities:
  • Path-based Routing: Maps URL paths to specific services
  • Host-based Routing: Routes traffic based on domain names
  • TLS Configuration: Specifies certificate resources for secure connections
  • Traffic Splitting: Can be used for canary deployments
  • Rewrite Rules: Modifies request URLs before forwarding
  • Annotation Support: Provides controller-specific configurations

Kubernetes Services

  • Role: Provides stable network identity and load balancing for pods
  • Responsibilities:
  • Service Discovery: Provides DNS names for sets of pods
  • Load Balancing: Distributes traffic among available pods
  • IP Management: Assigns stable virtual IPs to services
  • Port Mapping: Maps service ports to container ports
  • Session Affinity: Optional support for sticky sessions
  • Headless Services: Allows direct DNS lookup of pod IPs when needed
  • External Services: Can represent external endpoints when needed

Kubernetes Pods

  • Role: Houses application containers that process requests
  • Responsibilities:
  • Application Execution: Runs application code in containers
  • Request Processing: Handles business logic for API requests
  • Data Validation: Validates incoming request data
  • Authentication/Authorization: Verifies user permissions
  • Backend Integration: Communicates with databases and other services
  • Response Formation: Generates API responses
  • Resource Management: Works within allocated CPU/memory constraints
  • Health Reporting: Exposes health status to the cluster

TLS/SSL Certificate Configurations

Akamai Edge Certificates (Customer-Facing)

  • Type: Public CA-issued certificates (DigiCert, Let's Encrypt)
  • Purpose: Secures communication between clients and Akamai edge
  • Configuration:
  • Certificate Type: Usually wildcard or SAN certificates
  • Key Size: 2048-bit RSA or ECC P-256
  • Validity Period: Typically 1 year
  • Management: Automated through Akamai Certificate Manager
  • TLS Version: TLS 1.2/1.3 only
  • Cipher Suites: Modern, strong cipher suites only
  • OCSP Stapling: Enabled
  • HTTP Strict Transport Security (HSTS): Enabled

Akamai-to-Origin Certificates

  • Type: Public or Private CA certificates
  • Purpose: Secures communication between Akamai and NGINX Ingress
  • Configuration:
  • Certificate Type: Domain-specific certificate
  • Validation: Mutual TLS optional for additional security
  • Management: Automated with monitoring and alerts
  • Rotation: Regularly scheduled rotation (quarterly)
  • Key Storage: Secure key storage with restricted access
  • IP Restrictions: Typically limited to Akamai IP ranges

NGINX Ingress Controller Certificates

  • Type: Kubernetes-managed certificates via cert-manager
  • Purpose: Terminates TLS connections from Akamai and secures traffic
  • Configuration:
  • Certificate Source: Let's Encrypt or private CA
  • Validation: Domain validation automated
  • Storage: Kubernetes secrets
  • Rotation: Automated renewal before expiration
  • Key Size: 2048-bit RSA or ECC P-256
  • TLS Settings: Configured via ingress annotations
  • Secret References: Referenced in Ingress resources

Internal Service Mesh Certificates (Optional)

  • Type: Service mesh CA-issued certificates (e.g., Istio, Linkerd)
  • Purpose: Enables mTLS between services inside the cluster
  • Configuration:
  • Certificate Authority: Self-signed or intermediate CA
  • Workload Identity: Pod-specific certificates
  • Certificate Lifetime: Short-lived (24 hours typical)
  • Rotation: Automatic rotation before expiration
  • Key Generation: Generated on pod startup
  • Trust Chain: Managed by service mesh control plane

Certificate Renewal and Management Processes

  1. Monitoring:
  2. Automated certificate expiration monitoring
  3. Alerting at multiple thresholds (30, 14, 7, 3, 1 days)

  4. Certificate inventory database

  5. Automation:

  6. cert-manager for Kubernetes certificates
  7. Akamai certificate automation for edge certificates

  8. API-based renewal processes

  9. Emergency Procedures:

  10. Certificate revocation protocol
  11. Emergency replacement process
  12. Fallback certificates for critical services

  13. On-call rotation for certificate issues

  14. Audit and Compliance:

  15. Regular certificate inventory audits
  16. Compliance verification (key strength, algorithms)
  17. Certificate transparency monitoring

Security and Performance Considerations

TLS Termination Points and Re-encryption

  1. Client to Akamai Edge:
  2. First TLS termination at Akamai edge
  3. Modern TLS protocol and cipher suites

  4. Complete validation of client certificates if used

  5. Akamai to NGINX Ingress:

  6. Re-encrypted connection with separate certificate
  7. Potential for mutual TLS authentication
  8. IP-restricted access (Akamai edge IP ranges only)

  9. Private network path where possible

  10. Service Mesh Communication (Optional):

  11. Automatic mTLS between services
  12. Certificate-based service identity
  13. Encrypted east-west traffic within cluster

Network Security Controls

  1. Edge Security:
  2. IP reputation filtering
  3. Bot management
  4. DDoS protection
  5. API rate limiting
  6. Geo-blocking capabilities

  7. Custom WAF rules

  8. Cluster Network Security:

  9. Network policies for pod isolation
  10. Ingress/egress restrictions
  11. Service mesh traffic policies
  12. Namespace isolation

  13. Container network security

  14. Pod Security:

  15. Pod Security Policies/Standards
  16. Read-only file systems
  17. Non-root containers
  18. Dropped capabilities
  19. Resource limits

Headers and Metadata Transformation

  1. Client to Akamai:
  2. Client headers preserved
  3. Addition of request ID headers

  4. Security headers validation

  5. Akamai to Ingress:

  6. True-Client-IP headers added
  7. Client certificates translated to headers if used

  8. Custom security headers added

  9. Ingress to Service:

  10. Request transformation based on annotations
  11. Path rewriting if configured

  12. Additional application headers

  13. Service to Pod:

  14. Kubernetes service information
  15. Load balancer source preservation

  16. Original request metadata

  17. Response Path:

  18. Response headers added at each layer
  19. CORS headers managed
  20. Security headers enforced
  21. Cache control headers processed

Authentication and Authorization Enforcement

  1. Edge Authentication (Akamai):
  2. API key validation
  3. OAuth token pre-validation
  4. JWT signature verification

  5. Basic request authentication

  6. Ingress Authentication:

  7. External authentication service integration

  8. API gateway token validation

  9. Service-level Authentication:

  10. Service account tokens

  11. Internal service authentication

  12. Application Authentication:

  13. Detailed token validation
  14. Authorization policy enforcement
  15. Role-based access control
  16. Multi-tenancy enforcement

Performance Considerations and Bottlenecks

  1. Edge Performance:
  2. Global Akamai distribution
  3. Edge caching for appropriate responses
  4. Connection keep-alive

  5. Content compression

  6. Ingress Controller Performance:

  7. Controller scaling and redundancy
  8. Efficient routing algorithms
  9. Connection pooling

  10. Worker process optimization

  11. Service Routing Performance:

  12. Efficient service discovery
  13. Optimized iptables rules
  14. Kernel parameter tuning

  15. IPVS mode for kube-proxy

  16. Pod Performance:

  17. Proper resource allocation
  18. Horizontal scaling capability
  19. Efficient container images
  20. JVM/runtime optimization

Common Failure Points and Resilience Strategies

  1. Edge Failures:
  2. Multiple edge regions
  3. Failover configurations
  4. Health-based routing

  5. Origin shields

  6. Ingress Controller Failures:

  7. Controller redundancy
  8. Anti-affinity scheduling
  9. Failover configurations

  10. Health-based removal

  11. Service Discovery Failures:

  12. DNS caching strategies
  13. Short TTLs for critical services
  14. Direct endpoint access fallback

  15. Headless services when appropriate

  16. Pod Failures:

  17. Readiness/liveness probes
  18. Graceful shutdown handling
  19. PodDisruptionBudgets
  20. Topology spread constraints

  21. Horizontal Pod Autoscaling

  22. Backend Service Failures:

  23. Circuit breaking
  24. Retry budgets
  25. Fallback responses
  26. Cache-based resilience

Best Practices and Recommendations

Certificate Management

  1. Automated Lifecycle:
  2. Use cert-manager for Kubernetes certificates
  3. Implement automated renewal processes
  4. Monitor certificate expiration

  5. Maintain certificate inventory

  6. Security Best Practices:

  7. Use appropriate key lengths (RSA 2048+, ECC P-256+)
  8. Maintain secure private key storage
  9. Implement certificate pinning for critical services

  10. Regularly rotate certificates

  11. Operational Recommendations:

  12. Standardize on preferred CAs
  13. Document emergency certificate procedures
  14. Perform regular rotation drills
  15. Maintain certificate hierarchy diagram

Security Hardening

  1. Infrastructure Security:
  2. Keep Kubernetes version updated
  3. Apply security patches promptly
  4. Implement cluster hardening guidelines
  5. Use private networks where possible

  6. Enforce least privilege principles

  7. Application Security:

  8. Implement container security scanning
  9. Use distroless or minimal base images
  10. Perform regular vulnerability scanning

  11. Implement runtime threat detection

  12. Network Security:

  13. Default-deny network policies
  14. Implement microsegmentation
  15. Encrypt all traffic (east-west and north-south)
  16. Protect pod-to-pod communication

Performance Optimization

  1. Edge Optimization:
  2. Configure appropriate caching rules
  3. Implement content compression
  4. Use edge computing for simple transformations

  5. Configure connection pooling

  6. Kubernetes Optimization:

  7. Right-size pod resources
  8. Implement horizontal pod autoscaling
  9. Configure pod disruption budgets
  10. Optimize etcd performance

  11. Use node anti-affinity for critical services

  12. Application Optimization:

  13. Optimize container images
  14. Implement efficient API designs
  15. Use appropriate database indexes
  16. Optimize JVM settings for Java applications
  17. Implement response compression

Monitoring and Observability

  1. Infrastructure Monitoring:
  2. Kubernetes cluster monitoring
  3. Node and pod metrics
  4. Network traffic analysis

  5. Certificate expiration monitoring

  6. Application Monitoring:

  7. Request/response metrics
  8. Latency tracking
  9. Error rate monitoring

  10. Dependency health checks

  11. Request Tracing:

  12. Implement distributed tracing
  13. Maintain request IDs throughout the chain
  14. Trace context propagation

  15. Service dependency mapping

  16. Logging Strategy:

  17. Structured logging
  18. Centralized log aggregation
  19. Log level management

  20. Audit logging for security events

  21. Alerting and Dashboards:

  22. SLO-based alerting
  23. Multi-level alerting strategy
  24. Custom dashboards for different user roles
  25. Automated runbooks for common issues

References