Performance Testing Interview Question - Part 02

Performance Testing Interview Questions

Essential questions for load testing, JMeter, and performance analysis

Environment Issues Medium

3 min read July 12, 2023

If a test shows good results in lower environments but fails in production, what could be the causes?

Common causes for this discrepancy include:

• Environment differences: Production has different hardware, network configs, or data volumes
• Load characteristics: Production traffic patterns differ from test scenarios
• Third-party integrations: Mock services in test vs real integrations in production
• Configuration variances: Different caching, DB, or app server settings
• Data issues: Production data volume/characteristics not replicated in test

[Embed YouTube explanation video here]

Video coming soon with detailed analysis

Troubleshooting Hard

4 min read July 12, 2023

You observe a sudden drop in throughput during peak load with increasing response times. What steps will you take to identify the root cause?

Troubleshooting steps:

1. Check server resource utilization (CPU, memory, disk I/O, network)
2. Analyze application logs for errors or warnings
3. Examine database performance (query times, locks, deadlocks)
4. Review thread dumps for blocked threads
5. Check for external service dependencies slowing down
6. Monitor garbage collection activity
7. Verify connection pool settings and usage

[Embed YouTube explanation video here]

Video tutorial with real-world example

Testing Types Medium

5 min read July 12, 2023

What are the key differences between Load Testing, Stress Testing, Spike Testing, and Soak Testing?

Test Type	Purpose	Characteristics
Load Testing	Validate performance under expected load	Simulates normal user load, measures response times
Stress Testing	Find breaking points	Gradually increases load beyond limits, tests recovery
Spike Testing	Test sudden traffic bursts	Rapid load increase, measures how system handles spikes
Soak Testing	Identify memory leaks	Sustained load over long period (24+ hours)

[Embed YouTube explanation video here]

Visual comparison of test types

JMeter Easy

2 min read July 12, 2023

What is the role of the "Throughput Controller" in JMeter?

The Throughput Controller in JMeter:

• Controls how often its child elements are executed
• Two execution modes:
  • Percent Execution: Runs children a percentage of iterations
  • Total Executions: Runs children fixed number of times
• Useful for creating realistic user behavior patterns
• Example: Make login happen only 10% of iterations

[Embed YouTube explanation video here]

JMeter demo with Throughput Controller

JMeter/LoadRunner Hard

4 min read July 12, 2023

How do you handle dynamic correlation in JMeter or LoadRunner?

In JMeter:

1. Use Regular Expression Extractor or CSS/JQuery Extractor
2. Capture dynamic values from responses
3. Store in variables for subsequent requests
4. Use ${variable} syntax to reference them

In LoadRunner:

1. Use web_reg_save_param() function
2. Define left/right boundaries for value capture
3. Reference captured values as {paramName}

Best Practices:

• Verify captured values with debug samples
• Handle multiple matches when needed
• Consider boundary changes between releases

[Embed YouTube explanation video here]

Step-by-step correlation tutorial

Memory Analysis Hard

5 min read July 12, 2023

How do you identify and analyze a memory leak?

Identification:

• Monitor memory usage over time (soak testing)
• Look for steadily increasing memory that never drops
• Frequent garbage collection with little memory reclaimed

Analysis Tools:

• Java: VisualVM, Eclipse MAT, YourKit
• .NET: CLR Profiler, dotMemory
• General: Valgrind, PerfMon

Analysis Process:

1. Take heap dumps at intervals
2. Compare dumps to find growing objects
3. Analyze reference chains keeping objects alive
4. Identify root cause in application code

[Embed YouTube explanation video here]

Memory leak debugging walkthrough

Load Testing Medium

3 min read July 12, 2023

What is ramp-up time and how do you decide the optimal ramp-up?

Ramp-up time is the duration taken to start all virtual users in a load test.

Determining optimal ramp-up:

• General rule: Ramp-up = (Total users) / (Target users per second)
• Consider your application's expected real-world usage pattern
• For stress testing, use shorter ramp-up to find breaking points
• For realistic simulations, match expected traffic patterns
• Monitor system metrics to ensure ramp-up isn't too aggressive

Example: For 1000 users with target of 50 users/second → 20 second ramp-up

[Embed YouTube explanation video here]

Ramp-up configuration demo

© 2023 QA Interview Prep. All rights reserved.

Helping testers prepare for performance testing interviews.