Skip to content
intermediate Phase · Backend Performance

Latency

Measure and optimize response latency in backend systems.

35m
0 problems
Topic Progress 0%

Latency

What Is Latency?

Time for a request to travel and get a response.

Client → Network (50ms) → Server (100ms) → Network (50ms) → Client
Total latency: 200ms

Latency Sources

Source Typical
Network RTT 10-200ms
DNS 1-50ms
TLS handshake 1-2 round trips
Server processing 1-1000ms+

Key Points

  • Understanding Latency is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Latency Optimization

Components

  • Network: Round-trip time
  • Processing: Computation
  • Queueing: Wait time
  • Serialization: Encode/decode

Optimization

  • Caching
  • CDN
  • Connection pooling
  • Compression

Measurement

p50: 50ms
p95: 200ms
p99: 500ms

Best Practices

  • Set latency budgets
  • Monitor percentiles
  • Optimize hot paths

Key Points

  • Understanding Latency is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0 / 3 solved
Implement Latency

Design and implement a solution for Latency in a backend system. Consider scalability, error handling, and production readiness.

Solution 
// Latency implementation
// Key aspects: validation, error handling, logging, testing

public class Latency {
    // Production-ready implementation
}
Latency Edge Cases

Identify and handle edge cases for Latency. What happens under high load, with invalid input, or during failures?

Solution 
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotency
Latency Testing Strategy

Write a testing strategy for Latency. Include unit tests, integration tests, and performance tests.

Solution 
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. Latency is?

Question 1 options

2. Network RTT stands for?

Question 2 options

3. What is a common mistake when implementing Latency?

Question 3 options

Flashcards

Question

Latency?

Click to reveal answer

Answer

Time for request to travel and return

Question

RTT?

Click to reveal answer

Answer

Round-Trip Time

Question

Latency best practices

Click to reveal answer

Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1. Latency = time for request round trip
  • 2. Sources: network, DNS, TLS, processing
  • 3. Reduce: CDN, keep-alive, connection pooling

Interview Tips

  • • Measure and reduce latency
  • • Know latency sources

Cheat Sheet

Latency

  • Time for request to travel and return
  • Sources: network, DNS, TLS, server
  • Reduce: CDN, keep-alive, pooling