90+ Performance Test Engineer Interview Questions and Answers

Scenarios where issues with heap dump occur and recommendations for dev team

• Heap dump size is too large

• Heap dump is not generated at the right time

• Heap dump is not analyzed properly

• Heap dump is not shared with the right team members

• Recommendations: Optimize code to reduce memory usage, generate heap dump at appropriate times, analyze heap dump thoroughly, share heap dump with relevant team members

To gather NFR from an unaware client for a new application, follow these steps:

• Explain the importance of performance testing and its benefits

• Provide examples of how performance issues can impact the application and business

• Ask the client about their expectations for the application's performance

• Discuss the application's usage scenarios and expected user load

• Collaborate with the development team to identify potential performance bottlenecks

• Use industry standards and best pract...read more

Thread dumps are analyzed to identify performance bottlenecks and deadlocks in the application.

• To identify the root cause of performance issues

• To identify deadlocks and thread contention issues

• To identify long running threads and blocked threads

• To identify memory leaks and excessive CPU usage

• To identify issues related to garbage collection

• To identify issues related to database connections and transactions

Yes, virtual users can be reinitialized if they go to error state with consumable data.

• Reinitializing virtual users can help in identifying the root cause of the error.

• It is important to ensure that the consumable data is backed up before reinitializing the virtual users.

• Reinitializing virtual users should be done only after analyzing the error and identifying the cause.

• It is important to have a backup plan in case reinitializing the virtual users does not resolve the error.

Concurrent users and simultaneous users are often used interchangeably, but they have different meanings.

• Concurrent users refer to the number of users accessing the system at the same time.

• Simultaneous users refer to the number of users performing the same action at the same time.

• Concurrent users can perform different actions at the same time, while simultaneous users perform the same action.

• For example, if 100 users are accessing a website at the same time, they are concurre...read more

I am currently using the latest version of iOS on my iPhone, which is iOS 14.5.

• iOS 14.5 is the latest version of the operating system for iPhones

• Regular updates are important for security and performance improvements

Generating heap dump and thread dump on Unix/Linux systems

• For heap dump: use jmap command with -dump option

• For thread dump: use jstack command

• Heap dump can also be generated using kill -3

• Thread dump can also be generated using kill -QUIT

Test results report collates metrics related to performance, load, stress, and scalability testing.

• Response time

• Throughput

• Error rate

• CPU usage

• Memory usage

• Network usage

• Concurrent users

• Transactions per second

• Peak response time

• Peak throughput

• Peak error rate

CLI mode of testing involves using command line interface to execute tests. Correlation and parameterization can be done using Bean shell processes.

• CLI mode of testing involves running tests from the command line interface

• Correlation involves identifying dynamic values in the response and replacing them with variables

• Parameterization involves replacing hard-coded values with variables

• Bean shell processes can be used to write custom code for correlation and parameterization

• Exa...read more

Workload modeling involves designing a realistic simulation of user behavior and system usage.

• Identify user personas and their typical actions

• Determine the frequency and duration of each action

• Consider peak usage times and seasonal variations

• Use real-world data and historical trends to inform the model

• Validate the model through testing and iteration

I have used various tools for DB server tuning such as SQL Profiler, SQL Server Management Studio, and Database Engine Tuning Advisor.

• SQL Profiler for monitoring and analyzing SQL Server activity

• SQL Server Management Studio for managing and configuring SQL Server instances

• Database Engine Tuning Advisor for analyzing workload and recommending index and partitioning strategies

Questions related to JMeter execution, CSS selector, load testing, IDE and RC, correlation and parameterization.

• find element - returns the first matching element on the page, find elements - returns a list of all matching elements

• CSS selector - a pattern used to select and style HTML elements

• load testing - testing the system's ability to handle normal and expected loads

• spike testing - testing the system's ability to handle sudden and extreme increases in load

• stress testing - ...read more

Monolithic architecture is a single, self-contained unit while microservices architecture is a collection of small, independent services.

• Monolithic architecture is tightly coupled and difficult to scale.

• Microservices architecture is loosely coupled and can be scaled independently.

• Monolithic architecture has a single point of failure while microservices architecture is resilient to failures.

• Monolithic architecture is easier to develop while microservices architecture is more c...read more

NFR sheet can be prepared by identifying the non-functional requirements and documenting them in a structured format.

• Identify the non-functional requirements such as performance, scalability, reliability, security, usability, etc.

• Document the requirements in a structured format such as a spreadsheet or a table.

• Include details such as the requirement description, acceptance criteria, priority, and any dependencies.

• Ensure that the requirements are measurable and testable.

• Review...read more

I have experience with various protocols used in performance testing.

• HTTP/HTTPS

• TCP/IP

• FTP

• SMTP

• JMS

• SOAP

• REST

• WebSockets

Issues faced in Loadrunner scripting, execution, and reports

• Scripting: faced issues with correlation, parameterization, and dynamic data handling

• Execution: encountered problems with test environment setup, resource constraints, and test data management

• Reports: struggled with result analysis, performance bottlenecks identification, and report customization

There are several types of graphs, including line, bar, pie, scatter, and area graphs.

• Line graphs show trends over time.

• Bar graphs compare data between different categories.

• Pie graphs show proportions of a whole.

• Scatter graphs show the relationship between two variables.

• Area graphs show the cumulative totals over time.

A sampler is a component in JMeter that sends requests to a server and records the response.

• Samplers are used to simulate user requests to a server

• Throughput is the number of requests per unit of time

• Rampup is the time taken to reach the desired number of users

• Rampdown is the time taken to bring down the number of users to zero

• Post processors are used to extract data from the response and store it for future use

• Correlation is used to handle dynamic values in requests by extra...read more

Various error handling methods include try-catch blocks, exception handling, error codes, and logging.

• Try-catch blocks are used to catch and handle exceptions in code.

• Exception handling involves catching and handling specific types of exceptions.

• Error codes are used to identify and handle different types of errors.

• Logging is a method of recording errors and other relevant information for troubleshooting.

Correlation is a statistical measure that indicates the extent to which two or more variables are related.

• Correlation measures the strength and direction of the relationship between two variables.

• It ranges from -1 to +1, where -1 indicates a perfect negative correlation, +1 indicates a perfect positive correlation, and 0 indicates no correlation.

• Correlation is used in performance testing to identify the relationship between different performance metrics, such as response time...read more

Performance testing life cycle involves planning, preparation, execution, analysis, and reporting.

• 1. Planning phase involves defining objectives, scope, resources, and timelines.

• 2. Preparation phase includes creating test scenarios, scripts, and environment setup.

• 3. Execution phase involves running tests, monitoring performance metrics, and collecting data.

• 4. Analysis phase includes identifying bottlenecks, performance issues, and tuning recommendations.

• 5. Reporting phase inv...read more

I have executed load, stress, endurance, spike and scalability tests.

• Load testing to check system performance under normal and peak load conditions.

• Stress testing to identify system breaking point and measure its recovery time.

• Endurance testing to check system performance under sustained load conditions.

• Spike testing to check system performance under sudden load spikes.

• Scalability testing to check system performance under increasing load and measure its ability to scale.

Write a function to calculate the nth Fibonacci number.

• Create a function that takes an integer n as input

• If n is 0 or 1, return n

• Otherwise, return the sum of the previous two Fibonacci numbers

• Use recursion to call the function with n-1 and n-2 as inputs

LoadRunner is a performance testing tool with various components.

• Virtual User Generator (VuGen) - records and creates scripts

• Controller - manages and executes load tests

• Load Generators - simulates user load

• Analysis - analyzes test results

• Agent Process - collects data during test execution

Pacing time is calculated by dividing the total number of transactions by the duration of the test.

• Pacing time is used to determine the rate at which virtual users should be generated during a performance test.

• It is calculated by dividing the total number of transactions by the duration of the test.

• For example, if the test is scheduled to run for 1 hour and the expected number of transactions is 10,000, the pacing time would be 6 seconds (3600 seconds / 10,000 transactions).

Rendezvous point is a synchronization point in load testing where multiple virtual users wait for each other before proceeding.

• Used in load testing to simulate real-world scenarios

• Ensures that all virtual users reach a certain point before continuing

• Helps in measuring the response time of the system under load

• Can be used to test scenarios like online auctions, where multiple users bid at the same time

Error codes are generated during performance testing to indicate issues like server overload, timeouts, or resource limitations.

• Error codes can occur when the server response time exceeds the defined threshold, e.g., a 504 Gateway Timeout.

• High traffic can lead to 429 Too Many Requests errors, indicating the server is overwhelmed.

• Application errors, such as 500 Internal Server Error, can arise from unhandled exceptions during load testing.

• Resource limitations, like memory leak...read more