#load-balancing

Design load balancing and high availability systems for fault-tolerant, scalable application infrastructure. Load balancing strategies: 1. Application Load Balancer (ALB): Layer 7 routing, host/path-based routing, SSL termination. 2. Network Load Balancer (NLB): Layer 4 performance, static IP addresses, ultra-low latency. 3. Global load balancing: geographical distribution, DNS-based routing, CDN integration. Health checks: 1. HTTP health endpoints: /health returning 200 OK, comprehensive system status checks. 2. Check intervals: 30-second intervals, 3 consecutive failures for unhealthy marking. 3. Custom metrics: database connectivity, external service dependencies, resource availability. High availability design: 1. Multi-AZ deployment: minimum 2 availability zones, automatic failover mechanisms. 2. Auto Scaling Groups: CPU target 70%, predictive scaling for traffic patterns. 3. Circuit breaker pattern: fail fast when dependencies unavailable, graceful degradation. Performance optimization: 1. Connection pooling: database connections, HTTP keep-alive, connection limits. 2. Caching strategies: Redis/ElastiCache, CDN caching, application-level caching. 3. Content delivery: static assets via CDN, edge locations, cache invalidation strategies. Disaster recovery: 1. Cross-region replication: RTO < 4 hours, RPO < 1 hour for critical systems. 2. Backup strategies: automated daily backups, point-in-time recovery, cross-region backup storage. Traffic management: blue-green deployments, canary releases with 5% traffic initially, feature flags for instant rollback.