Load Testing

Load testing is a performance testing method that measures how an application or system behaves under expected levels of concurrent users and traffic.

Table of Contents

Table of Contents

What load testing measures

Load testing confirms that infrastructure and applications handle expected traffic. It differs from related performance tests in focus.

  • Load testing: expected, realistic levels of concurrent users
  • Stress testing: pushes systems past their limits to find breaking points
  • Volume testing: large amounts of data rather than many users

Key elements of a load test

  • Realistic scenarios: user journeys and load levels that match production
  • Representative data: test data that reflects real usage
  • Clear KPIs: response time, throughput, error rates, and resource use

How to run a load test

  1. Define the user scenarios and target load.
  2. Prepare test data and the target environment.
  3. Ramp traffic up to the target and hold it.
  4. Record response times, throughput, errors, and resource use.
  5. Compare results with targets and previous runs.

Common load testing patterns

Different patterns answer different questions about the same system.

Pattern Load shape Question it answers
Baseline Normal expected load Does the system meet targets day to day?
Spike Sudden bursts of traffic Can it absorb a flash sale or launch?
Soak Steady load for hours Do leaks or slowdowns appear over time?
Scalability Gradually rising demand Does autoscaling keep up?

Why load testing matters

Without load testing, performance problems often surface only in production. The result is outages, latency, and unhappy customers.

  • Autoscaling validation: confirm pods and nodes scale when traffic rises
  • Early regression detection: catch slowdowns in CI/CD before release
  • Reliable peaks: keep the customer experience steady during busy periods
  • Right-sized infrastructure: avoid paying for too much or too little capacity

Consider a SaaS company planning a product launch. A load test shows the login service slows past 2,000 concurrent users. The team adds capacity before launch, not during it.

Best practices for load testing

  • Test production-like environments: match infrastructure, data, and configuration
  • Set thresholds: define pass or fail limits for latency and errors
  • Ramp gradually: increase load in stages to spot the knee in the curve
  • Monitor the system: watch CPU, memory, and network alongside test metrics
  • Run continuously: load test on a schedule and in pipelines, not once a year

Real-world examples

  • Holiday readiness: an e-commerce platform runs JMeter load tests with Testkube across clusters before holiday sales
  • Streaming peaks: a streaming service simulates thousands of concurrent video requests to validate CDN performance

How load testing relates to Testkube

Testkube simplifies Kubernetes-native load testing. Load generators run next to the services they test.

  • Popular tools: JMeter, k6, and Artillery run directly inside clusters
  • Distributed load: executions scale across nodes for large simulations
  • CI/CD integration: continuous performance validation on every change
  • Observability: centralized dashboards and stored artifacts

Frequently Asked Questions (FAQs)

What is load testing?

Load testing measures how a system performs under expected levels of traffic and concurrent users.

What is the difference between load testing and stress testing?

Load testing uses expected traffic. Stress testing pushes beyond normal limits to find the breaking point.

Which metrics matter most in load testing?

Response time, throughput, error rate, and resource use. Latency percentiles show the slowest user experiences.

Which tools are used for load testing?

Popular open-source tools include JMeter, k6, Gatling, Locust, and Artillery.

Can load tests run in Kubernetes?

Yes. Testkube runs load tools inside clusters and spreads load across nodes.

How often should teams run load tests?

Run them in CI/CD for key services and on a schedule. Always test before major releases or traffic events.

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