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Caching

Dramatically reduce latency by storing frequently accessed data in fast memory

Low Latency Read Scaling Redis / Memcached CDN
Cache Tier Simulation ● Stopped
💻
Client
Last Key
⚡ Cache (RAM)
0/8
1ms access time
🗄️
Database
100ms access time
Queries
0
Idle
RECENT REQUESTS
0
Total Requests
0
Evictions
0ms
Avg Latency
0ms
Time Saved

Key Concepts

🎯 When to Use
  • Read-heavy workloads (>80% reads)
  • Expensive DB queries that repeat
  • Session data and user profiles
  • Static assets and computed results
⚖️ Trade-offs
  • Cache invalidation is hard
  • Stale data if TTL too long
  • Cache stampede on cold start
  • Memory is expensive vs disk
🎓 Interview Tips
  • Write-through vs write-back vs write-around
  • Cache stampede: probabilistic expiry, locks
  • L1/L2/L3 CPU cache = same concept
  • CDN is a cache at the network edge