Adapted from Mastering System Design from Basics to Cracking Interviews (Udemy) — https://www.udemy.com/course/mastering-system-design-from-basics-to-cracking-interviews/
1. Types of Performance Testing
Don't wait for production to fail. Use these testing strategies:
- Load Testing: Simulating expected daily usage to ensure the system meets its goals.
- Stress Testing: Pushing the system beyond its limits to see how it fails (and if it recovers).
- Spike Testing: Simulating sudden, massive bursts of traffic (e.g., a flash sale or viral post).
- Endurance Testing: Running a significant load over an extended period to find memory leaks or resource exhaustion.
2. Performance Monitoring & Observability
Monitoring is not testing. It is the continuous tracking of health metrics:
- APM (Application Performance Monitoring): Using tools like Datadog or New Relic to trace individual request spans.
- Infrastructure Metrics: Tracking CPU, Memory, Disk I/O, and Network saturation.
- Real User Monitoring (RUM): Tracking performance from the browser/client-side perspective.
3. Sudden Traffic Spikes: The Survival Guide
When traffic hits suddenly, a system must be architected for resilience:
- Autoscaling: Automatically spinning up new instances (AWS ASG or Kubernetes HPA).
- CDNs: Offloading static asset requests away from the origin server.
- Queueing: Using Kafka or SQS to "buffer" the burst so the backend can process it at a steady rate.
- Circuit Breakers: Stopping requests to failing components to prevent cascading failures.
Interview Questions & Answers 💡
1. How would you identify a system's performance bottleneck?
Identifying bottlenecks requires a systematic approach to tracing request flow and resource usage.
- Profiling: Use tools to break down the request path (DB calls, service-to-service). - Metric Correlation: Is CPU pegged while Disk I/O is low? Is there memory swapping? - Distributed Tracing: Locate slow operations across microservices using spans. - Stress Testing: Deliberately push the system to expose the weakest link.
2. What tools do you use for testing and monitoring?
- Testing: JMeter, k6, or Locust for load simulation.
- Monitoring: Prometheus + Grafana for metrics, ELK stack for logs, and New Relic/Datadog for APM.
3. How would you design a system to handle sudden traffic spikes?
A resilient system relies on elasticity and decoupling.
- Autoscaling: Scale vertically or horizontally based on real-time load. - Offloading: Use CDNs to serve static content at the edge. - Buffering: Use Message Queues (Kafka/SQS) to smooth out traffic spikes. - Statelessness: Ensure services can be scaled out instantly without local state issues.
Final Thoughts
A system that isn't tested is a system that will fail in production. Combine continuous monitoring with regular stress testing to build confidence in your architecture's scalability.
Back to basics? Revisit the foundational — Storage Basics