Web Cache - Scaling Considerations
Horizontal Scaling
Adding Cache Nodes
- Add nodes to handle increased traffic
- Consistent hashing for request distribution
- No data migration needed (stateless)
- Gradual traffic shift to new nodes
- Time to add node: <5 minutes
Load Balancing Strategies
- Geographic routing (GeoDNS)
- Round-robin with health checks
- Least connections
- Weighted distribution
- Sticky sessions for cache affinity
Cache Hit Rate Optimization
Improving Hit Rate
- Increase Cache Size: More storage = higher hit rate
- Optimize TTL: Longer TTL = more hits (trade-off: freshness)
- Cache Warming: Pre-populate popular content
- Request Coalescing: Reduce duplicate origin requests
- Compression: Store more content in same space
Hit Rate by Content Type
- Static assets: 95%+ (long TTL)
- HTML pages: 85%+ (moderate TTL)
- API responses: 70%+ (short TTL)
- Personalized content: 50%+ (user-specific caching)
Performance Optimization
Latency Reduction
- Multi-tier caching (memory + SSD)
- Compression (gzip, brotli)
- Connection pooling to origin
- HTTP/2 and HTTP/3 support
- Edge deployment (closer to users)
Throughput Improvement
- Parallel request processing
- Async I/O operations
- Zero-copy data transfer
- Efficient serialization
- Batch operations
Storage Scaling
Tiered Storage
- Hot tier (NVMe): <1ms, expensive
- Warm tier (SSD): <5ms, moderate cost
- Cold tier (HDD): <50ms, cheap
- Archive (S3): <100ms, very cheap
Storage Optimization
- Compression (3-5x space savings)
- Deduplication for identical content
- Automatic tier migration
- Cleanup of expired content
- Efficient metadata storage
Geographic Distribution
Multi-Region Deployment
- Deploy cache nodes in multiple regions
- Route users to nearest node
- Reduce cross-region latency
- Improve availability
- Comply with data residency
Cross-Region Coordination
- Invalidation propagation (<1s)
- Configuration synchronization
- Monitoring aggregation
- Failover between regions
Cache Stampede Prevention
Strategies
- Request Coalescing: Single origin fetch for duplicate requests
- Stale-While-Revalidate: Serve stale, refresh async
- Probabilistic Early Expiration: Refresh before TTL
- Cache Locking: First request fetches, others wait
Monitoring and Alerting
Key Metrics
- Hit rate, miss rate
- Latency (P50, P95, P99)
- Throughput (requests/sec)
- Error rate
- Resource utilization
Alerts
- Hit rate < 85%
- P99 latency > 10ms
- Error rate > 1%
- Disk usage > 90%
- Origin errors > 5%
This scaling guide ensures the web cache can handle growth while maintaining performance and reliability.