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Exam Professional Cloud Database Engineer All Questions

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Exam Professional Cloud Database Engineer topic 1 question 119 discussion

Actual exam question from Google's Professional Cloud Database Engineer
Question #: 119
Topic #: 1
[All Professional Cloud Database Engineer Questions]

You are the DBA of an online tutoring application that runs on a Cloud SQL for PostgreSQL database. You are testing the implementation of the cross-regional failover configuration. The database in region R1 fails over successfully to region R2, and the database becomes available for the application to process data. During testing, certain scenarios of the application work as expected in region R2, but a few scenarios fail with database errors. The application-related database queries, when executed in isolation from Cloud SQL for PostgreSQL in region R2, work as expected. The application performs completely as expected when the database fails back to region R1. You need to identify the cause of the database errors in region R2. What should you do?

  • A. Determine whether the versions of Cloud SQL for PostgreSQL in regions R1 and R2 are different.
  • B. Determine whether the database patches of Cloud SQI for PostgreSQL in regions R1 and R2 are different.
  • C. Determine whether the failover of Cloud SQL for PostgreSQL from region R1 to region R2 is in progress or has completed successfully.
  • D. Determine whether Cloud SQL for PostgreSQL in region R2 is a near-real-time copy of region R1 but not an exact copy.
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Suggested Answer: D 🗳️
by pk349 at Dec. 24, 2022, 10:15 p.m.

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chelbsik
Highly Voted 1 year, 11 months ago
Selected Answer: D
Verify that the replica has processed all the transactions it has received from the primary. This ensures that when promoted, the replica reflects all transactions that were received before the primary became unavailable. https://cloud.google.com/sql/docs/postgres/replication/cross-region-replicas#verify_failover_criteria
upvoted 7 times
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dynamic_dba
Highly Voted 1 year, 8 months ago
D. Since this is Cloud SQL, the versions and patch levels should be the same since it’s managed by Google. That eliminates A and B. The instance in region 2 must have been a read replica which was promoted to being the primary instance. You cannot access the new primary until Google completes the failover, so C doesn’t make sense. That leaves D. Basically, the data is slightly out of sync.
upvoted 5 times
pico
1 year, 3 months ago
You can have different patches https://cloud.google.com/sdk/gcloud/reference/sql/instances/patch
upvoted 1 times
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Pime13
Most Recent 6 months, 3 weeks ago
Selected Answer: C
https://cloud.google.com/sql/docs/postgres/replication/manage-replicas#promote-replica Before promoting a read replica, if the primary is still available and serving clients, you should do the following: Stop all writes to the primary instance. Check the replication status of the replica (follow the instructions in the psql Client tab). Verify that the replica is replicating, and then wait until the replication lag reported by the replay_lag metric is 0. Otherwise, a newly promoted instance may be missing some transactions that were committed to the primary instance.
upvoted 1 times
Zek
3 days, 6 hours ago
This explanation makes sense and would support D as the answer instead of C. Reason is because while the failover is in progress you would not be able to query the database and since some queries are successful, it suggest that the failover is complete. So it is possible that when the failover was done the replica lag on R2 was not 0 so that some transactions on the R1 were missing from the R2; hence the R2 may not have had an exact copy of the primary but a near realtime copy. I believe D is a more appropriate answer
upvoted 1 times
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learnazureportal
1 year, 2 months ago
The correct answer is - C. Determine whether the failover of Cloud SQL for PostgreSQL from region R1 to region R2 is in progress or has completed successfully.
upvoted 1 times
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DPonly
1 year, 2 months ago
Selected Answer: C
will go by C
upvoted 2 times
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pico
1 year, 3 months ago
Selected Answer: B
B Determine whether the database patches of Cloud SQL for PostgreSQL in regions R1 and R2 are different. This is important because differences in database patches could lead to inconsistencies in behavior between the two regions. Ensuring that the database patches are consistent between the two regions is essential for stable and expected behavior. D does not makes sense because the question specify that when executed in isolation from Cloud SQL for PostgreSQL in region R2, work as expected.
upvoted 1 times
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Nirca
1 year, 8 months ago
Selected Answer: C
If it was a DATA gap of data between the databases; The SQLs will not return "database-errors" just different data sets. Therefore I'm not going for D. Yet if the failover is ongoing/in-progress/hanging or not completed - than some stuff will work and other not. And we will get "database-errors" I'm going for C (A, B - versions should be managed by GCP)
upvoted 3 times
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pk349
1 year, 11 months ago
B : Determine whether the database *** patches of Cloud SQI for PostgreSQL in regions R1 and R2 are different
upvoted 1 times
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