How do you test web application performance during high traffic?

Metrics representations for Web applications are multifaceted and identifying the vital metrics should be biased on the monitoring objective at hand and often be used as a feedback loop for comprehending the application behavior under dynamic circumstances and continuously evolve the application based on these derived metric reports. Business metrics can quantify throughput, latency, error rate, availability, etc., Application metrics can quantify processor utilization, memory allocation rate, I/O calls, load balancing, and parallelism aspects

Simulating high traffic to test web application performance involves several key steps. Firstly, I'd evaluate the application's current performance metrics to establish a baseline. Then, using load testing tools like JMeter or Gatling, I'd create test scenarios mimicking high user traffic, gradually increasing the load to observe the application's response under stress. Additionally, I'd consider testing on various devices, browsers, and network conditions to ensure comprehensive coverage. This process helps identify potential bottlenecks, allowing for optimizations to enhance the application's overall performance and scalability.

To ensure traffic fairness without any external influence, an ideal place to conduct load, stress, and endurance tests on an application is the CICD build pipeline (that can be executed on demand as well) baselining on the acceptable thresholds, where the application artifact should be deployed to an ephemeral production-like environment and have diverse test scripts (varying parameters) executed against the deployed application and capture the metrics for reconciliation and set up alerts if there is deviation/anomaly from the historical test reports.

Nonfunctional requirements (NFR) should be mandated to be met for any desirable web application, and the captured metrics invariably lead to concluding whether these have been met or defaulted. For every code push/merge the application should be load, stress, and endurance tested this is attainable by ingraining the tests into the CICD pipeline and setting up alerts on result deviations from the previous/historical results. Further, the metrics should be used as a feedback mechanism for evaluating application behavior and identifying potential hotspots requiring investigation and remediation.