Google PCA Practice Question: Managing Implementation and Ensuring Solution and Operations Reliability
Your company uses Cloud Spanner in a multi-region configuration to achieve 99.999% availability. You need to understand the impact of a regional failure on read and write availability. Which statement is correct?
⚠ Common exam trap
PCA often tests the misconception that synchronous replication equals write availability everywhere — candidates forget that only the leader accepts writes and pick 'both reads and writes fully available'.
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
✓
Writes are unavailable if the region containing the leader replica fails, but reads remain available
Cloud Spanner multi-region configurations use a leader replica in one region and read-only replicas in others. Writes must go through the leader (Paxos quorum), so if the region hosting the leader fails, writes are unavailable until a new leader is elected — typically within seconds to minutes depending on the config. Reads, however, can be served from any healthy replica (strong or stale reads), so read availability is preserved as long as at least one replica region survives.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Both reads and writes are fully available as long as at least one region remains healthy
Why it's wrong here
Writes require majority; one region may not be enough.
- ✗
Reads and writes remain fully available because Cloud Spanner uses synchronous replication across all regions
Why it's wrong here
Synchronous replication still requires majority for writes.
- ✓
Writes are unavailable if the region containing the leader replica fails, but reads remain available
Why this is correct
Cloud Spanner's leader replica handles all writes, so a regional failure affecting that leader halts writes until a new leader is elected. Reads, however, are served by any replica, so they continue from surviving regions, satisfying the stem's read-versus-write availability distinction.
- ✗
Writes are always available, but reads may be unavailable if the region with the closest replica fails
Why it's wrong here
Writes are not always available if majority is lost.
Go deeper
Related to this question
Key term
Regional
Regional refers to a deployment strategy where cloud resources are distributed across multiple geographic areas to improve availability, reduce latency, and meet compliance requirements.
Key term
Cloud Spanner
Cloud Spanner is a fully managed, globally distributed relational database service from Google Cloud that combines the benefits of relational database structure with horizontal scalability and strong consistency.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
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