latency-optimization

# Latency Optimization

Comprehensive guide to reducing end-to-end latency in distributed systems - from network to application to database layers.

## When to Use This Skill

- Optimizing response times for user-facing applications
- Creating latency budgets for distributed systems
- Implementing geographic routing strategies
- Reducing database query latency
- Optimizing API response times
- Understanding and measuring latency components

## Latency Fundamentals

### Understanding Latency

```text
Latency Components:

Total Latency = Network + Processing + Queue + Serialization

┌─────────────────────────────────────────────────────────────┐
│                     Request Journey                          │
│                                                              │
│  Client ──► DNS ──► TCP ──► TLS ──► Server ──► DB ──► Back  │
│                                                              │
│  Components:                                                 │
│  ├── DNS Resolution: 0-100ms (cached: 0ms)                  │
│  ├── TCP Handshake: 1 RTT (~10-200ms)                       │
│  ├── TLS Handshake: 1-2 RTT (~20-400ms)                     │
│  ├── Request Transfer: depends on size                       │
│  ├── Server Processing: application-specific                 │
│  ├── Database Query: 1-1000ms typical                       │
│  └── Response Transfer: depends on size                      │
└─────────────────────────────────────────────────────────────┘

Key Metrics:
- P50: Median latency (50th percentile)
- P95: 95th percentile (tail latency starts)
- P99: 99th percentile (important for SLOs)
- P99.9: Three nines (critical systems)
```

### Latency Numbers Every Developer Should Know

```text
Latency Reference (2024 estimates):

Operation                              Time
─────────────────────────────────────────────────────
L1 cache reference                     1 ns
L2 cache reference                     4 ns
Branch mispredict                      5