Trade-offs & Alternatives

📖 3 min read 📄 Part 7 of 10

Web Cache - Trade-offs and Alternatives

Caching Strategies

Cache-Aside vs Write-Through

Cache-Aside (Lazy Loading): ✅ Only cache what's requested ✅ Resilient to cache failures ❌ Cache miss penalty ❌ Potential stale data

Write-Through: ✅ Always consistent ✅ No cache misses ❌ Higher write latency ❌ Wasted cache space

TTL vs Event-Based Invalidation

TTL-Based: ✅ Simple, automatic ✅ Predictable behavior ❌ May serve stale data ❌ May evict fresh data

Event-Based: ✅ Always fresh data ✅ Efficient invalidation ❌ Complex implementation ❌ Requires event infrastructure

Storage Trade-offs

Memory vs Disk

Memory Cache: ✅ Ultra-low latency (<1ms) ✅ High throughput ❌ Limited capacity ❌ Expensive per GB ❌ Volatile (lost on restart)

Disk Cache: ✅ Large capacity ✅ Persistent ✅ Cost-effective ❌ Higher latency (5-50ms) ❌ Lower throughput

Compression Trade-offs

Compressed Storage: ✅ 3-5x space savings ✅ Reduced bandwidth ❌ CPU overhead ❌ Decompression latency

Uncompressed: ✅ No CPU overhead ✅ Faster serving ❌ More storage needed ❌ Higher bandwidth

Consistency Trade-offs

Strong vs Eventual Consistency

Strong Consistency: ✅ Always fresh data ✅ No stale reads ❌ Higher latency ❌ Lower availability ❌ Complex coordination

Eventual Consistency: ✅ Low latency ✅ High availability ✅ Simple implementation ❌ Temporary stale data ❌ Invalidation lag

Alternative Architectures

Varnish vs Nginx vs Squid

Varnish:

  • In-memory caching
  • VCL configuration language
  • Excellent for static content
  • Limited disk caching

Nginx:

  • Reverse proxy + cache
  • Simple configuration
  • Good all-around performance
  • Limited cache management

Squid:

  • Forward + reverse proxy
  • Disk-based caching
  • Complex configuration
  • Good for large objects

CDN vs Self-Hosted Cache

CDN (CloudFlare, Akamai): ✅ Global edge network ✅ DDoS protection ✅ Managed service ❌ Vendor lock-in ❌ Higher cost at scale ❌ Less control

Self-Hosted: ✅ Full control ✅ Lower cost at scale ✅ Custom features ❌ Operational overhead ❌ Limited edge locations ❌ No DDoS protection

Eviction Policy Trade-offs

LRU vs LFU vs FIFO

LRU (Least Recently Used): ✅ Simple, effective ✅ Adapts to access patterns ❌ One-time access can evict useful data

LFU (Least Frequently Used): ✅ Better for skewed patterns ✅ Keeps popular content ❌ Slow to adapt ❌ Higher overhead

FIFO (First In First Out): ✅ Simplest implementation ✅ Predictable behavior ❌ Ignores access patterns ❌ Poor hit rate

This analysis helps in making informed decisions based on specific requirements and constraints.