Load Testing

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Load Testing is a specialized performance testing that you use to assess the performance (e.g. page load times and processing times) and stability (e.g. error-free operation with a specific number of users) of your system under expected and peak load conditions. It involves subjecting the system to a number of virtual (simulated) users or transactions to measure its latency, response time, throughput, resource usage, and scalability.

Examples of Load Testing

• You perform Load Testing on an e-commerce website to determine how it handles concurrent user requests during peak shopping seasons (for instance Thanksgiving in the USA or Diwali in India), ensuring that the system remains responsive and can handle the expected workload.
• In a video streaming platform, you conduct Load Testing to evaluate the platform's ability to deliver high-quality videos to multiple users simultaneously, without buffering or  degradation of resolution or audio quality.
• For a banking system, you can use Load Testing to validate the system's response time and stability when processing a large number of financial transactions in a short period, such as during salary transfers or tax filing seasons.

Tips for Load Testing

• First, identify the most frequently executed or performance-critical business processes in your software.
  
• Identify realistic load scenarios that reflect the expected user behavior and transaction volume, considering factors such as peak usage periods, geographical distribution, and user actions.
• Popular tools for Load Testing include Apache JMeter, LoadRunner, Gatling, and Locust, which provide features for simulating concurrent user traffic, generating realistic load scenarios, and analyzing performance metrics.
  
• When you run a load scenario, monitor key performance indicators (KPI) like network and software latency, response time, throughput, CPU and memory utilization, and database performance, to identify performance bottlenecks (areas for improvement).
• Gradually increase the load in your load scenario to simulate realistic workload and observe how the system handles the increasing demand, helping to uncover scalability limitations.
• Conduct Load Testing on a production-like environment that closely resembles the actual production setup to obtain accurate performance insights and avoid discrepancies due to different hardware or configurations.
  

FAQ (interview questions and answers)

1. What is the purpose of Load Testing?
   Assess how a system performs under expected and peak load conditions, assessing if it can handle the anticipated user traffic, transactions, or data volume while maintaining acceptable performance levels.
2. Is it necessary to perform Load Testing for every software application?
   No, but it is useful for applications that are expected to experience high usage or have critical performance requirements, such as e-commerce platforms, banking systems, and applications with a large user base.
3. Can Load Testing uncover scalability issues in a system?
   Yes, Load Testing is an effective way to identify scalability issues in a system. By gradually increasing the load and measuring the system's performance, Load Testing can reveal bottlenecks (like resource limitations, or architectural flaws) that may impact the system's ability to handle increased user demand.

Remember to just comment if you have any doubts or queries.