80+ 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.

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

Thread states in thread dump include NEW, RUNNABLE, BLOCKED, WAITING, TIMED_WAITING, and TERMINATED.

• NEW: thread has been created but not yet started

• RUNNABLE: thread is executing or ready to execute

• BLOCKED: thread is blocked waiting for a monitor lock

• WAITING: thread is waiting indefinitely for another thread to perform a particular action

• TIMED_WAITING: thread is waiting for another thread to perform a particular action for a specified period of time

• TERMINATED: thread has compl...read more

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

Load Runner and JMeter are performance testing tools used to measure the performance of web applications.

• Load Runner is a licensed tool developed by Micro Focus that supports a wide range of protocols and technologies.

• JMeter is an open-source tool developed by Apache that supports HTTP, FTP, JDBC, and other protocols.

• Both tools simulate user traffic and measure the response time, throughput, and resource utilization of the application.

• Load Runner has a user-friendly interface...read more

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

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 experience with various protocols used in performance testing.

• HTTP/HTTPS

• TCP/IP

• FTP

• SMTP

• JMS

• SOAP

• REST

• WebSockets

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.

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.

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

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

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

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).

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.

Bug is a coding mistake while error is a deviation from expected behavior.

• Bug is a mistake in the code that causes unexpected behavior.

• Error is a deviation from expected behavior.

• Bug is a result of a mistake made by a programmer.

• Error can be caused by a variety of factors such as hardware failure, network issues, or user input.

• Bug can be fixed by modifying the code while error requires identifying and resolving the underlying cause.

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

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

I have worked on various monitoring tools such as JMeter, LoadRunner, and Gatling.

• JMeter for load testing web applications

• LoadRunner for performance testing client-server applications

• Gatling for stress testing and real-time monitoring

IP Spoofing is a technique used to impersonate another device by changing the source IP address of a packet.

• IP Spoofing is commonly used in DDoS attacks to hide the attacker's identity.

• It can also be used to bypass access controls by impersonating a trusted device.

• IP Spoofing can be prevented by using firewalls and network intrusion detection systems.

Parameterization is the process of replacing hard-coded values in a test script with variables to make it more flexible and reusable.

• Parameterization helps in creating data-driven tests

• It allows us to test the same functionality with different sets of data

• It reduces the need for creating multiple test scripts for similar scenarios

• Examples of parameterization include using CSV files, databases, or spreadsheets to provide test data

3-tier architecture is a client-server architecture with three layers: presentation, application, and data storage.

• Presentation layer: User interface for interaction with the application

• Application layer: Business logic and processing of user requests

• Data storage layer: Storage and retrieval of data

• Each layer communicates with the layer above and below it

• Allows for scalability and separation of concerns

• Examples: Web applications, e-commerce sites, banking systems

Use lr_trim_string function to remove trailing and leading spaces in Loadrunner

• Use lr_trim_string function to remove leading and trailing spaces

• Syntax: lr_trim_string("string", "both", " ")

• Example: lr_trim_string(" example ", "both", " ") will return "example"

Load Runner and JMeter are both performance testing tools, but differ in their scripting languages and pricing models.

• Load Runner uses its own proprietary scripting language, while JMeter uses Java

• Load Runner is a commercial tool with licensing fees, while JMeter is open source and free

• Load Runner has a more user-friendly interface, while JMeter requires more technical expertise

• Both tools can simulate high user loads and measure system performance

Performance testing helps identify bottlenecks, optimize system performance, and ensure reliability under different load conditions.

• Identify performance bottlenecks in the system

• Optimize system performance to improve user experience

• Ensure system reliability under different load conditions

• Validate scalability of the system

• Helps in determining the maximum capacity of the system

• Identify potential issues before they impact end users

Threads are lightweight processes within a process that can run concurrently. Thread groups are a collection of threads.

• Threads are independent sequences of execution within a process.

• Thread groups are used to organize and manage multiple threads together.

• Threads within a group can share resources and communicate with each other.

• Example: In performance testing, threads can simulate multiple users accessing a system concurrently.

SLA in performance testing refers to the agreed upon level of service that a system must meet in terms of response time, throughput, and other performance metrics.

• SLA stands for Service Level Agreement

• It defines the expected performance metrics that a system must meet

• SLAs are typically agreed upon between stakeholders and are used to measure the performance of a system

• Examples of SLAs include response time should be less than 2 seconds, throughput should be at least 100 trans...read more

A performance test plan is a document that outlines the objectives, scope, approach, and resources required for conducting performance testing.

• Defines the goals and objectives of the performance testing

• Specifies the scope of the testing, including the systems, components, and functionalities to be tested

• Outlines the test approach, including the tools, techniques, and methodologies to be used

• Identifies the performance metrics and success criteria

• Defines the test environment an...read more

To record a script in SAP using performance testing tools like Neoload or LoadRunner, certain settings need to be configured.

• Configure the recording settings in the performance testing tool to record SAP transactions

• Ensure that the SAP client and server are properly configured for recording

• Set up the proxy settings in the performance testing tool to capture the SAP traffic

• Verify that the recording is capturing the desired SAP transactions accurately

Thread dump can be taken using tools like jstack, jcmd, or through the application server console.

• jstack command can be used to take thread dump of a Java process running on the machine.

• jcmd command can be used to take thread dump of a Java process running on the machine.

• Application server console can also be used to take thread dump.

• Thread dump helps in identifying the threads that are consuming more CPU time or are stuck in a deadlock.

Android testing is the process of testing applications developed for the Android operating system.

• It involves testing the functionality, performance, and usability of Android apps.

• Testing can be done manually or using automated tools like Espresso, UI Automator, and Robolectric.

• Types of testing include unit testing, integration testing, and acceptance testing.

• Common testing challenges include device fragmentation, compatibility issues, and security concerns.

To upload and capture a bug, use a bug tracking tool and follow a standardized process.

• Use a bug tracking tool like JIRA or Bugzilla to log the bug

• Provide detailed steps to reproduce the bug

• Include screenshots or videos to help explain the issue

• Assign the bug to the appropriate team member for resolution

• Follow up on the bug until it is resolved and closed

SDLC stands for Software Development Life Cycle.

• It is a process followed by software development teams to design, develop, test, and deploy software.

• It includes phases like planning, analysis, design, implementation, testing, and maintenance.

• It helps in ensuring that the software is developed efficiently and meets the requirements of the stakeholders.

• It is a framework that helps in managing the software development process.

• It is also known as the software development process ...read more

Correlation is the process of extracting dynamic values from server responses and passing them to subsequent requests. Parameterization is the process of replacing hard-coded values in scripts with variables.

• Correlation involves identifying and capturing dynamic values such as session IDs, tokens, or timestamps from server responses.

• Parameterization involves replacing hard-coded values in scripts with variables to make scripts reusable and dynamic.

• Correlation is essential for...read more

Bottlenecks can be identified through performance testing and monitoring.

• Conduct load testing to simulate real-world usage

• Monitor system resources such as CPU, memory, and disk usage

• Analyze response times and error rates

• Identify slow database queries or network latency

• Use profiling tools to identify code-level bottlenecks

• Prioritize and address bottlenecks based on impact and severity

Passion for optimizing software performance and ensuring user satisfaction.

• Enjoy analyzing system behavior under load

• Passionate about optimizing software performance

• Fascinated by the impact of performance on user experience

Load generator in LR simulates virtual users to generate load on the application under test.

• Load generator simulates virtual users by sending requests to the application under test.

• It helps in generating load on the application to measure performance.

• Load generator can be configured to simulate different types of user behaviors and scenarios.

• It collects performance metrics and generates reports for analysis.

• Examples: JMeter, LoadRunner, Gatling.

Scripting challenges include dynamic parameters, correlation, and handling complex scenarios.

• Dynamic parameters require capturing and replacing values in scripts

• Correlation involves identifying and handling dynamic values in responses

• Complex scenarios require careful planning and scripting to ensure accurate simulation

• Debugging and troubleshooting can be time-consuming and require attention to detail

Monitoring in SAP application involves using tools like SAP Solution Manager, SAP CCMS, and third-party monitoring tools.

• Use SAP Solution Manager to monitor system performance, availability, and configuration.

• Leverage SAP CCMS (Computer Center Management System) for real-time monitoring of SAP systems.

• Utilize third-party monitoring tools like Dynatrace, AppDynamics, or New Relic for end-to-end monitoring of SAP applications.

• Set up alerts and notifications to proactively addre...read more

Yes, I am willing to join on client location if required.

• I am open to joining on client location for the duration of the project

• I understand the importance of being on-site for effective communication and collaboration

• I have previous experience working on client location for performance testing projects