Lab: Identify and Quantify the Workload [Needs Clarification]

The title of this lab is “Identify and Quantify the Workload”, however the question is “Which queries are the top 3 most qualitatively important for designing the data model?”

When I select (what I think are) the 3 most quantitatively important important operations, based on data size and frequency, it’s marked as a wrong answer, so I guess we really do mean qualitative importance?

However I don’t understand how to determine the qualitative importance of a given operation, and having watched the previous lecture several times, I can’t see where this is explained. Searching the www hasn’t provided an answer either. Any pointers or references would be most gratefully received.

Thank you

Simon

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Hey @Simon_39939

Think of it more without the adverb. And just ask yourself

  1. What are the most important query/writes that this app relies on
  2. Then what query/writes happen the most.

As you said:

Thanks @natac13, but I’m still not sure I get it. In my mind, qualitative means “this fruit bowl contains apples, pears and bananas, so you should put the bananas somewhere else because they give off ethylene which can cause the other fruit to over-ripen”, whereas quantitative means “this fruit bowl contains 70% apples, 20% bananas and 10% pears, but bananas are consumed twice as fast as apples so you should buy more bananas”.

Are you suggesting that I should forget about the difference between the two?

Your point 1 - by “important”, do you mean the operations without which the application cannot provide any business value? Now I’ve seen the detailed answer for this lab, it doesn’t seem to take this factor into account.

And your point 2 - the detailed answer does take frequency of the operations into account (both average and peak), but it also considers whether the operation is real-time, whether it requires low latency and the size of the data. I’m unable to reverse engineer from the detailed answer a set of rules to decide in which order all these factors should be considered in order to determine the overall importance of an operation.

In the M201 performance course, when looking at how to optimise indexes, we were given the rule “equality, sort, range”, i.e. to create an index which is optimised for a particular query, index first on the fields which the query tests for equality, then on the fields which the query uses to sort the results, and finally on the fields which the query tests for things like greater than, less than or $in. This is a nice, simple, easy to remember rule which has served me well when creating indexes.

Am I over-simplifying things by expecting a similar rule for which factors to take into account and in what order, when deciding which are the most important operations?

Yep pretty much; What query/writes are required to make that application work.

And from Google

qual·i·ta·tive

  1. relating to, measuring, or measured by the quality of something rather than its quantity.

describing the quality of something in size, appearance, value, etc. Such adjectives can be submodified by words such as very and have comparative and superlative forms

So I was thinking it would mean the quality; in this case how important something is. Not so much the different ‘kinds’ as you mentioned here.

I see in the definition that it mentions size and appearance but I think it is more how good are the fruits in the bowl, regardless of what kind they are.

No, please do not take it that way. I was just trying to help simplify the process as I was struggling with this Lab as well. And I only figured it out when I understood that it is about the importance of the event.
Consider a user login (low frequency) vs logs giving status on the page health (high frequency). The higher importance I would think is the login?

OK thanks. Agreed that if a user can’t log in then the application is useless, whereas if we don’t have any information about the health of the application then our operations team won’t be too happy, but it doesn’t prevent the application from being useful.

If we both struggled with this lab then I guess the MongoDB University folks need to consider revisiting and updating this lecture. I’d be interested to hear their thoughts on this subject (and I appreciate that it’s a Saturday afternoon and we can’t expect them to be monitoring this forum 24x7). In the meantime I’ll just continue with the subsequent chapters and hope I have a light bulb moment at some point.

Agreed! The question in itself is unclear; i.e. the structure of the sentence; and the use of the word “qualitatively” makes it even more unclear.

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Plus one that. It is confusing.