Practice Test 2 | Google Cloud Certified Professional Data Engineer | Dumps | Mock Test
Your company uses Google Cloud as its main platform. The lead architect decided to migrate the architecture’s relational databases to Cloud Spanner for horizontal scaling and multi-regional availability. Upon using Cloud Spanner for a while after migration and monitoring its performance, it was reported Cloud Spanner instance’s performance is not as expected as in the planning phase. What could be a possible reason for this? (Choose 2).
A. UUID is used as primary keys for the tables.
B. Primary keys are monotonically increased.
C. Primary keys are randomly generated 16-byte alphanumericals.
D. Primary key used is a combination of timestamp and original primary key as #timestamp-pk.
Answer: B & D.
Description:
Cloud Spanner uses compute nodes to read and write data. Tables data is stored lexicographically by primary key. Data is distributed among multiple storage “splits.”
This is the reason why choosing the right primary key for Cloud Spanner is important for performance. If primary key is monotonic, this leads to storing table data to one storage split, which in return leads to compute nodes to hit the same storage split for reading & writing. A good primary key is a key which helps evenly distributing data among different storage splits.
Source(s):
Choosing the Right Primary Keys (TIL about Cloud Spanner):
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