Sr. Performance Test Engineer Screening Exam

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Customer says they need 95th percentile response time value for all transactions. Your scenario has 10 virtual users which you know will generate at least 90 observations for each transaction. Your colleague says you must change your scenario to ensure 95th percentile can be calculated. You decide to:
Your test scenario has 200 vusers. Beyond 50 vusers, you notice that response times stayed the same but Total transactions per second and Throughput (bytes) went down. You decide to:

  1. Imagine a small store with a single clerk and an area for browsing products and no one leaves without buying something.  A customer enters the store, browses available products, selects one of them, pays for it at the counter and then exits the store.  Assume that this is a stable system (the arrival rate at which people enter the store is the same as their exit rate) and think time is defined as time spent by customers browsing the products before getting in line to pay for their selection.


If 30 customers were seen entering the store in a 60-minute interval and each customer spent 10 minutes in the store before leaving, what was the average number of customers in the store during this time? 

IP spoofing configuration
Select the statement that is false.
During a 10 minute interval, you observe a JEE application server processing requests at a rate of 40 per second.  You also know that a request requires 0.02 seconds to process.  The application server has 8 processors and 256 GB RAM.  What is the overall utilization of the system?
Given the following definitions for a storage system:
A:  Time taken to service an I/O request by a disk excluding wait time
B:  Total response time
C:  B - A
What is the relationship between HTTP, TCP and IP protocols?
Given the following definitions-

Think time: Time spent by users between successive requests to a system
Throughput: Rate of requests processed by a system in requests/second
Response time: Time elapsed from the moment users submit a request until they receive a response
Imagine a web application that has three completely independent subsystems.  You run a performance test, and find out that the failure rates of the three subsystems are as follows:
A - 2%
B - 3%
C - 4%

What can you say about the overall reliability of the system (assume that reliability refers to the system returning valid responses)
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