Latency

What I do

• Measure and analyze network latency
• Identify latency sources in systems
• Design low-latency architectures
• Optimize data transfer protocols
• Implement caching strategies
• Reduce round-trip times
• Profile application performance

When to use me

Use me when:

• Diagnosing slow network performance
• Building real-time applications
• Designing distributed systems
• Optimizing user experience
• Understanding network bottlenecks
• Planning capacity and scaling

Key Concepts

Latency vs Bandwidth

• Latency: Time for single packet (ms)
• Bandwidth: Data per second (Mbps)
• They affect performance differently:
  • Latency critical for interactive apps
  • Bandwidth critical for bulk transfers

Speed of Light Limits

• Fiber: ~200,000 km/s (2/3 c)
• Theoretical minimum latency = distance / speed
• Example: NYC to London ~70ms minimum

Latency Components

Total Latency = 
  ┌─────────────────┐
  │ Processing      │  (routers, switches)
  │ + Serialization │  (bits on wire)
  │ + Propagation   │  (distance/speed of light)
  │ + Transmission  │  (bandwidth limits)
  │ + Queuing       │  (congestion)
  └─────────────────┘

Measurement Tools

• ping: RTT to host
• traceroute: Path and per-hop latency
• WebPageTest: Full page load analysis
• Chrome DevTools: Network timing
• APM tools: Application latency tracking

Common Latency Targets