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Home Forums AWS AWS Certified Database – Specialty Formulation about question on replication lag query

  • Formulation about question on replication lag query

  • Benny25

    November 11, 2023 at 3:14 am


    So I don’t know if the formulation is weird or I am not aware of a feature. There is the following question:

    <pre data-renderer-start-pos=”170″>A company has an enterprise application hosted in an Amazon ECS cluster and uses Amazon RDS for MySQL database with a read replica. The application uses the read replica to generate business reports and avoid performance issues on the primary DB instance. However, the users noticed that the queries to the read replica have a high replication lag.
    Which of the following is the MOST likely root cause of this issue?

    The formulation of the question implies that, when doing normal query we see that replication lag is high, which means that we can detect replication lag while doing normal query.

    Except if there is a feature I am not aware of, this is incorrect.

    You can query the slave to get replication lag, or even better get it from your metrics, but you can not have it part of a normal query.

    Can you confirm me if replication lag can actually be returned as part of normal query?

    If not, I would suggest to update the question to change the formulation.

  • Carlo-TutorialsDojo

    November 14, 2023 at 11:27 pm

    Hello Benny,

    Thanks for your insight.

    I’d like to clarify that replication lag as a metric is not something an end-user can directly measure, rather it’s the effects of it, like delayed updates, that they might experience.

    I understand that the way the question is constructed seems to imply that replication lag as a metric is something that can be seen by users, which isn’t the case. We’ll review this item and make the necessary changes to clarify it.

    Let me know if you have further questions.


    Carlo @ Tutorials Dojo

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