Traffic Management & Reliability

Learn how to design robust systems that can handle high traffic volumes, balance loads effectively, and maintain reliability even during failures.

Quick Reference

Load Balancer Selection

  • Application Load Balancer (ALB): HTTP/HTTPS, path-based routing, microservices
  • Network Load Balancer (NLB): TCP/UDP, ultra-low latency, static IP needs
  • Least Connections: Varied request times, long-lived connections
  • Round Robin: Equal capacity servers, stateless applications
  • Health checks: Always configure for production systems

Rate Limiting Best Practices

  • Token Bucket: Allows bursts while maintaining long-term rate
  • Use client identification: API key, user ID, or IP address
  • Include clear rate limit headers in responses
  • Implement tiered limits for different user types
  • Consider distributed implementation for clustered services

Fault Tolerance Patterns

  • Circuit Breaker: Prevent cascading failures, fail fast, protect services
  • Retry with backoff: For transient failures, add jitter to prevent retry storms
  • Bulkhead Pattern: Isolate failures with resource partitioning
  • Fallbacks: Graceful degradation for critical functionality
  • Health checks: Detect failures before they impact users

System Design Interview Tips

When discussing traffic management and reliability in your interview, be sure to address these key points:

Scalability Architecture

Explain how your traffic management approach supports both vertical and horizontal scaling. Discuss how load balancers, API gateways, and service discovery enable seamless scaling without client awareness or downtime.

Failure Handling

Clearly articulate your system's failure modes and how they're addressed. Explain circuit breakers, retries, and fallbacks in the context of your specific design, showing how partial failures don't cascade to total system outage.

Resource Protection

Demonstrate awareness of protecting finite resources using rate limiting, bulkheads, and throttling. Explain how your design prevents resource exhaustion during traffic spikes or partial outages.

Monitoring & Recovery

Discuss how your system detects failures through health checks and monitoring, and the automated recovery mechanisms that restore service. Explain how observability is built into the design to quickly identify and address issues.