Exam Professional Data Engineer topic 1 question 129 discussion

Should be B

B The questions is specifically about organizing the data in BigQuery and storing backups.

Snapshot decorators in BigQuery allow you to query a table at a past point in time, but they are limited by BigQuery’s time travel window (which is typically 7 days). Since errors are sometimes only detected after 2 weeks, snapshot decorators won’t be effective for recovering data beyond their retention period.

With Storage Decorators, BigQuery only stores the differences between a snapshot and its base table, minimizing storage costs.

D is the most cost optimized solution to keep the backup. please read the link - https://cloud.google.com/bigquery/docs/table-snapshots-intro#table_snapshots

I think D is better.

The best option is D. Organize your data in separate tables for each month, and use snapshot decorators to restore the table to a time prior to the corruption.

Answer is D: Snapshots are different from time travel. They can hold data as long as we want. Furthermore "BigQuery only stores bytes that are different between a snapshot and its base table" so pretty cost effective as well. https://cloud.google.com/bigquery/docs/table-snapshots-intro#table_snapshots

From : https://cloud.google.com/architecture/dr-scenarios-for-data#BigQuery It can't be D If the corruption is caught within 7 days, query the table to a point in time in the past to recover the table prior to the corruption using snapshot decorators. Store the original data on Cloud Storage. This allows you to create a new table and reload the uncorrupted data. From there, you can adjust your applications to point to the new table. => D

D - this solution in integrated. No core is needed

90% of questions are having multiple answers and its very hard to get into every discussion where the conclusion is not there

The answer is B: Why not D? Because snapshot costs can become high if a lot of small changes are made to the base table: https://cloud.google.com/bigquery/docs/table-snapshots-intro#:~:text=Because%20BigQuery%20storage%20is%20column%2Dbased%2C%20small%20changes%20to%20the%20data%20in%20a%20base%20table%20can%20result%20in%20large%20increases%20in%20storage%20cost%20for%20its%20table%20snapshot. Since the question specifically states that the ETL pipeline is regularly modified, this means that lots of small changes are present. In combination with the requirement to optimize for storage costs, this means that option B is the way to go.

keyword: detected after 2 weeks. only snapshot could resolve the problem.

From BigQuery documentation - Benefits of using table snapshots include the following: - Keep a record for longer than seven days. With BigQuery time travel, you can only access a table's data from seven days ago or more recently. With table snapshots, you can preserve a table's data from a specified point in time for as long as you want. - Minimize storage cost. BigQuery only stores bytes that are different between a snapshot and its base table, so a table snapshot typically uses less storage than a full copy of the table. So storing data in GCS will make copies of data for each table. Table snapshots are more optimal in this scenario.

Organizing your data in separate tables for each month will make it easier to identify the affected data and restore it. Exporting and compressing the data will reduce storage costs, as you will only need to store the compressed data in Cloud Storage. Storing your backups in Cloud Storage will make it easier to restore the data, as you can restore the data from Cloud Storage directly

Organize in separate tables and store in GCS

D "With BigQuery time travel, you can only access a table's data from seven days ago or more recently. With table snapshots, you can preserve a table's data from a specified point in time for as long as you want." [source: https://cloud.google.com/bigquery/docs/table-snapshots-intro]