20+ Performance Engineer Interview Questions and Answers

Throughput measures the amount of data transferred per unit time, while hits/sec measures the number of requests served per second.

• Throughput is measured in bytes/sec or bits/sec, while hits/sec is measured in requests/sec.

• Throughput is affected by network bandwidth, while hits/sec is affected by server processing power.

• To design spike testing in LoadRunner, use the 'Ramp-up' feature to gradually increase the load over time.

• In JMeter, use the 'Thread Group' element to specify...read more

Load average is the average number of processes in the run queue over a period of time.

• Load average is a metric that measures the average number of processes that are either in a running or uninterruptable sleep state.

• It is calculated over a period of time, usually 1, 5, or 15 minutes.

• The load average is displayed as three numbers, which represent the load average for the past 1, 5, and 15 minutes, respectively.

• Commands that give the load average metric include 'uptime', 'top...read more

There are several types of performance testing such as load testing, stress testing, endurance testing, spike testing, and scalability testing.

• Load testing: testing the system's ability to handle a specific load

• Stress testing: testing the system's ability to handle beyond its capacity

• Endurance testing: testing the system's ability to handle a sustained load over a long period of time

• Spike testing: testing the system's ability to handle sudden spikes in traffic

• Scalability test...read more

Mobile UI response times can be captured using various tools and techniques.

• Use profiling tools like Android Profiler or Xcode Instruments

• Implement custom logging to capture timestamps for UI events

• Use network monitoring tools to capture network requests and responses

• Perform manual testing and use a stopwatch to measure response times

• Use automated testing tools like Appium or Selenium to capture response times

• Consider using third-party performance monitoring tools like New Re...read more

Linux commands for monitoring

• top - displays system processes

• htop - interactive process viewer

• vmstat - virtual memory statistics

• iostat - input/output statistics

• netstat - network statistics

• sar - system activity report

• free - displays memory usage

• df - displays disk space usage

• ps - displays information about running processes

Network bandwidth constraint in testing refers to limitations on the amount of data that can be transmitted over a network during testing.

• Network bandwidth constraint can impact the performance of an application or system being tested.

• It can lead to slow response times, timeouts, or even failures during testing.

• Examples of network bandwidth constraints include limited bandwidth on a shared network, network congestion, or network latency.

• Performance engineers need to consider ...read more

Java program to find 2nd largest element in an array of strings

• Convert array elements to integers for comparison

• Sort the array in descending order

• Return the element at index 1 as the 2nd largest element

Python script to capture system resources

• Use psutil library to access system resources

• Collect CPU, memory, disk, and network usage data

• Display the captured resources in a readable format

Timers in JMeter are used to simulate real user behavior by adding delays between requests.

• Timers help in controlling the load on the server by adding delays between requests.

• They can be used to simulate realistic user behavior by adding random or constant delays.

• Examples of timers in JMeter include Constant Timer, Gaussian Random Timer, and Uniform Random Timer.

URL mode is used to test the performance of a specific URL, while HTML mode is used to test the performance of the entire HTML page.

• URL mode focuses on a single URL, measuring response time and other metrics specific to that URL.

• HTML mode simulates user behavior on the entire HTML page, including loading all resources like images, scripts, and stylesheets.

• URL mode is useful for pinpointing performance issues with specific URLs, while HTML mode provides a more comprehensive vi...read more

PTLC stands for Performance Testing Life Cycle, which is a process followed in performance testing to ensure the performance of a system.

• PTLC involves planning, preparation, execution, and analysis of performance tests.

• It includes defining performance goals, creating test scenarios, executing tests, and analyzing results.

• PTLC helps in identifying performance bottlenecks and optimizing system performance.

• Example: In PTLC, performance engineers use tools like JMeter or LoadRunn...read more

Use the 'hostname' command in a shell script to find the hostname of the system.

• Use the 'hostname' command in a shell script to directly print the hostname of the system.

• You can store the output of the 'hostname' command in a variable for further processing.

• Example: hostname=$(hostname) - This will store the hostname in the 'hostname' variable.

Locators in Selenium are used to identify web elements on a web page. They are essential for interacting with elements during test automation.

• Locators are used to find and interact with web elements on a web page.

• Common types of locators include ID, name, class name, tag name, link text, and XPath.

• Using the right locator strategy is crucial for stable and reliable test automation.

• Example: driver.findElement(By.id("username"));

The challenge in analysis is to identify the root cause of performance issues.

• Identify the performance metrics to be analyzed

• Collect and analyze data from various sources

• Use tools like APM, profiling, and monitoring tools

• Identify patterns and anomalies in the data

• Correlate the data to identify the root cause

• Provide recommendations for improvement

Performance testing procedures for API involve load testing, stress testing, and scalability testing.

• Conduct load testing to determine how the API performs under normal and peak load conditions.

• Perform stress testing to evaluate the API's stability and reliability under extreme conditions.

• Conduct scalability testing to assess the API's ability to handle increased workload by adding more resources.

• Monitor response times, throughput, and error rates during testing to identify p...read more

Function user for correlate is used to correlate two or more sets of data.

• It is used in performance testing to correlate the data between the client and server.

• It helps in identifying the performance bottlenecks and improving the overall performance.

• Examples of data that can be correlated include session IDs, transaction IDs, and user IDs.

PT (Physical Therapy) is required to help patients recover from injuries, surgeries, or chronic conditions by improving mobility, strength, and function.

• PT helps improve range of motion and flexibility.

• It can help reduce pain and inflammation.

• PT can prevent future injuries by strengthening muscles and improving balance.

• It is essential for post-operative rehabilitation to regain function and mobility.

• PT can also help manage chronic conditions like arthritis or back pain.

Different types of performance testing include load testing, stress testing, and scalability testing.

• Load testing: Evaluates system performance under normal and peak load conditions.

• Stress testing: Tests system performance beyond its normal capacity to identify breaking points.

• Scalability testing: Measures system's ability to handle increased workload by adding resources.

• Endurance testing: Checks system performance over an extended period to ensure stability.

• Spike testing: Te...read more

Root Cause analysis in PY involves identifying the underlying reason for performance issues.

• Identify the symptoms of the performance issue

• Gather data and metrics related to the performance problem

• Analyze the data to pinpoint the root cause

• Implement solutions to address the root cause

Reverse a given number program

• Take the input number

• Initialize a variable to store the reversed number

• Loop through the digits of the input number from right to left

• Add each digit to the reversed number variable

• Print the reversed number

To find the 2nd highest salary in SQL, use the 'SELECT TOP 1' statement with 'ORDER BY salary DESC OFFSET 1'.

• Use the 'SELECT TOP 1' statement to retrieve the highest salary.

• Order the salaries in descending order using 'ORDER BY salary DESC'.

• Use 'OFFSET 1' to skip the first highest salary and retrieve the second highest salary.

APM tools are commonly used in Performance Testing to monitor and analyze the performance of applications under load.

• APM tools help in identifying performance bottlenecks and optimizing application performance.

• Examples of popular APM tools include New Relic, Dynatrace, AppDynamics, and Datadog.

• These tools provide real-time monitoring, alerting, and performance analytics to help improve application performance.

• APM tools can track key performance metrics such as response time, ...read more