PCDE Plan and manage database infrastructure Practice Question

Exhibit

CREATE TABLE Users (
  UserId INT64 NOT NULL,
  Name STRING(MAX),
) PRIMARY KEY (UserId);

Refer to the exhibit. This DDL is used to create a table in Cloud Spanner. The table will be used for storing user data with high write throughput. What is one performance issue with this table design?

⚠ Common exam trap

A common misconception is that any integer primary key is acceptable, but in Cloud Spanner, monotonically increasing keys create hotspots because all writes are directed to a single split, limiting write throughput.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The primary key is a monotonically increasing integer

Using a monotonically increasing integer as the primary key in Cloud Spanner causes all writes to be directed to a single split (tablet), creating a hotspot that severely limits write throughput. Cloud Spanner distributes splits across nodes based on key ranges, and sequential keys prevent this distribution, leading to performance degradation under high write load.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
The primary key is a monotonically increasing integer
Why this is correct
Sequential keys cause write hotspots in Spanner, leading to uneven load.
✗
The Name column is of type STRING(MAX)
Why it's wrong here
STRING(MAX) is valid and does not inherently cause performance issues.
✗
There are no secondary indexes
Why it's wrong here
Lack of indexes affects reads but not write throughput directly.
✗
The table is not interleaved with another table
Why it's wrong here
Interleaving is optional and not related to this performance issue.

Go deeper

PCDE Plan and manage database infrastructure Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

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