easyMultiple Choice
Google PCA Practice Question: A developer needs to cache session state for a…
A developer needs to cache session state for a web application to reduce latency. The cache must be highly available and support sub-millisecond access times. Which Google Cloud service should they use?
⚠ Common exam trap
PCA often tests the distinction between in-memory caching services and persistent databases, so candidates might incorrectly choose Firestore or Bigtable due to familiarity, overlooking the sub-millisecond latency requirement that only Memorystore for Redis satisfies.
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
✓
Memorystore for Redis
Memorystore for Redis is a fully managed in-memory data store service on Google Cloud, providing sub-millisecond latency for read and write operations. It supports high availability through replication and automatic failover, making it ideal for caching session state in web applications. Other options like Firestore, Cloud Storage, and Bigtable are not in-memory and cannot guarantee sub-millisecond access times.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Firestore
Why it's wrong here
Firestore is a document database whose reads traverse a persistent storage layer, so latency exceeds the sub-millisecond in-memory requirement. It is tempting as a managed, highly available store for session data, but Memorystore Redis is the purpose-built in-memory cache for this workload.
- ✗
Cloud Storage
Why it's wrong here
Cloud Storage is object storage accessed over HTTP, with latency in milliseconds and no in-memory caching semantics, so it cannot meet sub-millisecond session reads. It is tempting for durable session persistence, but Memorystore Redis provides the in-memory, highly available cache this scenario requires.
- ✗
Bigtable
Why it's wrong here
Bigtable is a wide-column NoSQL database for high-throughput analytical and time-series workloads, not an in-memory cache, so it cannot deliver sub-millisecond session reads. It would suit large-scale key-range scans; Memorystore Redis provides the in-memory, highly available caching this scenario requires.
- ✓
Memorystore for Redis
Why this is correct
Memorystore for Redis delivers sub-millisecond latency through in-memory storage, and its standard tier provides automatic failover across zones, satisfying the high-availability constraint. Persistent disk options such as Filestore or Cloud SQL cannot match in-memory read speeds, so Redis is the only listed service meeting both the latency and availability requirements.
Go deeper
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Key term
Caching
Caching is the process of storing copies of frequently accessed data in a temporary storage location, known as a cache, so that future requests for that data can be served faster and with less computational effort.
Key term
Redis
Redis is an open-source, in-memory data structure store used as a database, cache, and message broker for high-speed data access.
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JA
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
This PCA 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 PCA exam.