Design innovative, scalable, and highly available cloud database solutions →easyMultiple ChoiceObjective-mapped
PCDE Practice Question: Design innovative, scalable, and highly available cloud database solutions
Which Spanner feature allows you to add a new column to an existing table without blocking writes or requiring a rebuild?
⚠ Common exam trap
Google Cloud often tests the distinction between concurrency control mechanisms (like optimistic locking) and schema management features, leading candidates to confuse a transaction isolation technique with a DDL operation that supports zero-downtime schema changes.
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
✓
Online DDL
Online DDL (Data Definition Language) in Spanner allows schema changes such as adding a new column to an existing table without blocking writes or requiring a full table rebuild. This is achieved through a non-blocking, multi-phase schema update process that applies changes in the background while the table remains fully available for reads and writes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Optimistic locking
Why it's wrong here
Used for transactions, not schema changes.
- ✓
Online DDL
Why this is correct
Spanner's schema updates are online and non-blocking.
- ✗
Interleaved tables
Why it's wrong here
This is a table structure, not a DDL feature.
- ✗
Schema versioning
Why it's wrong here
Not a feature of Spanner.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCDE exam.