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Exam Professional Data Engineer topic 1 question 58 discussion

Actual exam question from Google's Professional Data Engineer
Question #: 58
Topic #: 1
[All Professional Data Engineer Questions]

You architect a system to analyze seismic data. Your extract, transform, and load (ETL) process runs as a series of MapReduce jobs on an Apache Hadoop cluster. The ETL process takes days to process a data set because some steps are computationally expensive. Then you discover that a sensor calibration step has been omitted. How should you change your ETL process to carry out sensor calibration systematically in the future?

  • A. Modify the transformMapReduce jobs to apply sensor calibration before they do anything else.
  • B. Introduce a new MapReduce job to apply sensor calibration to raw data, and ensure all other MapReduce jobs are chained after this.
  • C. Add sensor calibration data to the output of the ETL process, and document that all users need to apply sensor calibration themselves.
  • D. Develop an algorithm through simulation to predict variance of data output from the last MapReduce job based on calibration factors, and apply the correction to all data.
Show Suggested Answer Hide Answer
Suggested Answer: B 🗳️
by [deleted] at March 21, 2020, 11:31 a.m.

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SteelWarrior
Highly Voted 4 years, 2 months ago
Should go with B. Two reasons, it is a cleaner approach with single job to handle the calibration before the data is used in the pipeline. Second, doing this step in later stages can be complex and maintenance of those jobs in the future will become challenging.
upvoted 58 times
Yiouk
3 years, 3 months ago
B. different MR jobs execute in series, adding 1 more job makes sense in this case.
upvoted 7 times
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[Removed]
Highly Voted 4 years, 8 months ago
Answer: A Description: My take on this is for sensor calibration you just need to update the transform function, rather than creating a whole new mapreduce job and storing/passing the values to next job
upvoted 20 times
Jphix
3 years, 6 months ago
It's B. A would involving changing every single job (notice it said jobS, plural, not a single job). If that is computationally intensive, which it is, you're repeating a computationally intense process needlessly several times. SteelWarrior and YuriP are right on this one.
upvoted 11 times
mark1223jkh
6 months, 1 week ago
Why all jobs, change only the first job for calibration, right?
upvoted 1 times
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Marwan95
Most Recent 4 months, 3 weeks ago
Selected Answer: A
I'll choose A. WHY? cause the process already takes DAYS and adding another step will increase the time more
upvoted 1 times
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jin0
1 year, 9 months ago
What kinds of sensor calibrations exists? I don't understand how computation in pipeline would be expense due to calibration being omitted..?
upvoted 1 times
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samdhimal
1 year, 10 months ago
B. Introduce a new MapReduce job to apply sensor calibration to raw data, and ensure all other MapReduce jobs are chained after this. This approach would ensure that sensor calibration is systematically carried out every time the ETL process runs, as the new MapReduce job would be responsible for calibrating the sensors before the data is processed by the other steps. This would ensure that all data is calibrated before being analyzed, thus avoiding the omission of the sensor calibration step in the future. It also allows you to chain all other MapReduce jobs after this one, so that the calibrated data is used in all the downstream jobs.
upvoted 1 times
samdhimal
1 year, 10 months ago
Option A is not ideal, as it would be time-consuming to modify all the transformMapReduce jobs to apply sensor calibration before doing anything else, and there is a risk of introducing bugs or errors. Option C is not ideal, as it would rely on users to apply sensor calibration themselves, which would be inefficient and could introduce inconsistencies in the data. Option D is not ideal, as it would require a lot of simulation and testing to develop an algorithm that can predict the variance of data output accurately and it may not be as accurate as calibrating the sensor directly.
upvoted 1 times
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DipT
1 year, 11 months ago
Selected Answer: B
It is much cleaner approach
upvoted 1 times
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DGames
1 year, 11 months ago
Selected Answer: B
Best approach is calibration will be separate job because if we need to tune the calibration later also it would be to maintain without worries about all other jobs.
upvoted 1 times
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odacir
1 year, 11 months ago
Selected Answer: B
Should be B. My reason, this is like an Anti corruption layer, and that's a good practice, C- , if you modify your transformMapReduce will be harder to test and debug, so it's a bad practice. C the idea de introduce manual operation is an anti patron and has a lot of problems D It's overkilling, a don't have sense in this scenario.
upvoted 1 times
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ZIMARAKI
2 years, 10 months ago
Selected Answer: B
SteelWarrior explanation is correct :)
upvoted 3 times
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lord_ryder
2 years, 10 months ago
Selected Answer: B
SteelWarrior explanation is correct
upvoted 1 times
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medeis_jar
2 years, 10 months ago
Selected Answer: B
SteelWarrior explanation is correct
upvoted 1 times
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hendrixlives
2 years, 11 months ago
Selected Answer: B
SteelWarrior's answer is correct
upvoted 1 times
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anji007
3 years, 1 month ago
Ans: B Adding a new job in the beginning of chain makes more sense than updating existing chain of jobs.
upvoted 1 times
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sumanshu
3 years, 5 months ago
Vote for 'B' (introduce new job) over 'A', (instead of modifying existing job)
upvoted 5 times
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YuriP
4 years, 3 months ago
Should be B. It's a Data Quality step which has to go right after Raw Ingest. Otherwise you repeat the same step unknown (see "job_s_" in A) number of times, possibly for no reason, therefore extending ETL time.
upvoted 5 times
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[Removed]
4 years, 8 months ago
It's between A or B. Should choose A
upvoted 4 times
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