Load testing distributed web services - George Malamidis, loveholidays

Load testing at scale requires simulating real user behavior rather than just hitting endpoints with synthetic traffic

Using production access logs for load testing provides realistic traffic patterns and helps validate system behavior under load

Load testing distributed systems requires handling complex scenarios like retries, failovers, and graceful degradation

Tools should compensate for timing drifts and delays when replaying traffic at higher rates than originally recorded

Monitor key metrics like latency (P50/P99), throughput, error rates and resource utilization during load tests

Start with lower traffic multiples (1-5x) before ramping up to higher loads (10x+) to identify bottlenecks gradually

Consider downstream dependencies and external services - either mock them or ensure they can handle the increased load

Use canary deployments, feature flags and proper monitoring to safely test in production environments

Load testing is not just for performance validation but also helps train engineers on system behavior under stress

Combine load testing with other reliability practices like chaos engineering and proper observability for comprehensive validation