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CCNA Pcdoe Manage Databases Questions

25 of 175 questions · Page 3/3 · Pcdoe Manage Databases topic · Answers revealed

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151
MCQeasy

A Cloud SQL for MySQL instance is running low on disk space. You have enabled automatic storage increase, but you also want to be proactively alerted when disk usage exceeds 80%. Which steps should you take?

A.Set the storage size to a fixed large value to avoid alerts.
B.Create a Cloud Logging sink for disk usage logs and set up a Pub/Sub notification.
C.Create a Cloud Monitoring alert on the metric 'disk/utilization' with a threshold of 80%.
D.Use Cloud SQL's built-in email notifications for disk usage.
AnswerC

This is the correct way to get an alert when disk usage exceeds 80%.

Why this answer

Cloud Monitoring allows you to create alerting policies based on metrics. The disk usage metric for Cloud SQL is available, and you can set a threshold of 80%. Automatic storage increase is a separate setting that automatically increases storage when needed.

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152
MCQeasy

A company is using Cloud Firestore to store user profiles. They need to query users by both their 'age' and 'city' fields. What must they configure to perform this query efficiently?

A.Use Firestore in Datastore mode for automatic composite indexes.
B.Configure index exemptions for the fields.
C.No configuration needed; single-field indexes are sufficient.
D.Create a composite index on age and city.
AnswerD

Composite index is required for queries on multiple fields.

Why this answer

Firestore automatically creates single-field indexes for simple queries. However, for queries filtering on multiple fields like 'age' and 'city', a composite index must be created manually. Option B is correct.

Option A (single-field index) is insufficient. Option C (index exemptions) is for arrays and maps, not for multi-field queries. Option D (Datastore mode) does not change this requirement.

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153
MCQeasy

A startup is building a mobile application and needs a real-time database that automatically scales to handle sudden spikes in user traffic. They want to minimise operational overhead and only pay for the resources they use. Which Google Cloud database should they choose?

A.Firestore
B.Cloud Spanner
C.Cloud SQL
D.Cloud Bigtable
AnswerA

Firestore is serverless, auto-scaling, and pay-per-use, ideal for mobile apps.

Why this answer

Firestore is a fully managed, serverless NoSQL document database that automatically scales horizontally to handle sudden traffic spikes without manual intervention. It offers real-time data synchronization via listeners, and its pay-per-use billing model aligns with the startup's requirement to minimize operational overhead and only pay for consumed resources.

Exam trap

Cisco often tests the misconception that Cloud Spanner is the best choice for any scalable database need, but candidates overlook that Spanner requires provisioned capacity and is not serverless, while Firestore's auto-scaling and pay-per-use model directly address the startup's requirements for minimizing operational overhead and handling sudden spikes.

How to eliminate wrong answers

Option B is wrong because Cloud Spanner is a globally distributed, strongly consistent relational database designed for high-throughput OLTP workloads, but it requires upfront capacity planning and incurs costs for provisioned nodes, not a pay-per-use model, making it unsuitable for a startup wanting to minimize overhead and pay only for usage. Option C is wrong because Cloud SQL is a managed relational database (MySQL, PostgreSQL, SQL Server) that does not auto-scale for sudden spikes; it requires manual or scheduled scaling of read replicas and has a fixed instance size billing model, not a consumption-based model. Option D is wrong because Cloud Bigtable is a wide-column NoSQL database optimized for large-scale analytical and operational workloads (e.g., time-series, IoT) with high throughput, but it requires manual cluster sizing and pays for provisioned nodes per hour, not a serverless pay-per-use model, and lacks real-time data synchronization features.

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154
MCQeasy

A developer is setting up a Memorystore for Redis instance and needs to restrict access to only a specific Compute Engine VM in the same VPC network. Which configuration should they use?

A.Use Cloud Armor to whitelist the VM's external IP
B.Use the AUTH password and share it only with the VM
C.Configure the Memorystore instance with a firewall rule that allows only the VM's internal IP
D.Place the Redis instance in a separate VPC and peer only with the VM's VPC
AnswerC

Correct. Firewall rules can be applied to the VPC to restrict inbound traffic to the Memorystore instance's IP range from only the VM's IP.

Why this answer

Memorystore for Redis uses Private Service Access with VPC peering. Access control is via authorized networks (VPC networks) and optionally by using Cloud Armor or firewall rules at the VM level. The simplest is to authorize the VM's VPC network and then use a firewall rule to allow traffic only from the specific VM's IP.

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155
Multi-Selectmedium

You are designing a disaster recovery plan for a Cloud Bigtable instance. The instance has a single cluster in us-east1. You need to ensure that if the cluster becomes unavailable, the database can still serve read and write requests with minimal downtime. Which THREE steps should you take? (Choose three.)

Select 3 answers
A.Ensure the application can handle eventual consistency between clusters.
B.Enable synchronous replication between clusters.
C.Add a second cluster in a different zone (e.g., us-east1-b) and enable replication.
D.Configure the application to route traffic to the secondary cluster in case of primary failure.
E.Take a full backup of the table to Cloud Storage daily.
AnswersA, C, D

Bigtable replication is asynchronous, so occasional stale reads are possible.

Why this answer

Option A is correct because Cloud Bigtable uses eventual consistency for replication across clusters. When you add a second cluster and enable replication, data is replicated asynchronously, meaning writes to one cluster are not immediately visible in the other. The application must be designed to handle eventual consistency to avoid reading stale data after a failover.

Exam trap

Cisco often tests the misconception that synchronous replication is available in Cloud Bigtable, but the service only supports asynchronous replication, and candidates may also incorrectly think that daily backups are sufficient for high availability instead of using multi-cluster replication.

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156
MCQeasy

Your Cloud Bigtable instance is experiencing high latency for certain row key ranges. You suspect a hotspot is developing. Which Google Cloud tool should you use to visualize and diagnose the hotspot?

A.Key Visualiser
B.Cloud Monitoring dashboard to check CPU utilization per node
C.Bigtable's built-in 'hotspot detection' alert in Cloud Monitoring
D.Cloud Logging to review request logs and identify slow queries
AnswerA

Key Visualiser is the correct tool for detecting hotspots in Bigtable.

Why this answer

Key Visualiser is a tool specifically designed for Bigtable to identify hotspots and access patterns by visualizing row key distribution and traffic. It helps pinpoint uneven load distribution.

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157
Multi-Selecteasy

A company is using Cloud Spanner and wants to back up a database to Cloud Storage for long-term retention. They also need to restore the database to a specific point in time within the last 7 days. Which two features should they use? (Choose TWO.)

Select 2 answers
A.Set up a cross-region replica for backup
B.Use Spanner's point-in-time recovery feature to restore to a specific timestamp
C.Enable version management on the Spanner instance
D.Export the database using gcloud spanner databases export
E.Create a backup of the Spanner database using gcloud spanner backups create
AnswersB, E

Spanner allows restoring to a specific time within the retention period.

Why this answer

Spanner supports creating backups and restoring from them. Backups can be stored in Cloud Storage (as part of the backup process) and can be used for point-in-time recovery within a configurable retention period (up to 7 days by default).

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158
MCQeasy

A Cloud SQL for PostgreSQL instance is running low on disk space. The database size is 500 GB and the current storage is 600 GB. The engineer needs to increase storage to 800 GB without downtime. What should they do?

A.Shut down the instance, edit the configuration to increase storage, then restart.
B.Use gcloud sql instances patch to increase storage size to 800 GB.
C.Create a new instance with 800 GB storage and migrate data using pg_dump.
D.Enable auto-storage increase and wait for it to happen automatically.
AnswerB

The patch command can increase storage online without downtime.

Why this answer

Option B is correct because Cloud SQL for PostgreSQL supports online storage increases using the `gcloud sql instances patch` command, which resizes the disk without requiring an instance restart or downtime. The storage can be increased up to the maximum allowed for the instance tier, and the change takes effect immediately while the instance remains available.

Exam trap

Cisco often tests the misconception that storage changes require downtime or instance restart, leading candidates to choose the shutdown option (A) instead of the online patch command (B).

How to eliminate wrong answers

Option A is wrong because shutting down the instance causes downtime, which violates the requirement for zero downtime; Cloud SQL allows storage increases without stopping the instance. Option C is wrong because creating a new instance and migrating with pg_dump involves significant downtime during the dump and restore process, and is unnecessarily complex when a simple online resize is available. Option D is wrong because auto-storage increase only triggers when storage usage reaches a threshold (typically 90% or more), and it increases storage by a fixed increment (e.g., 10 GB or 15% of current size), not to a specific target like 800 GB; it also may not activate immediately and does not guarantee the exact desired size.

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159
MCQmedium

A Memorystore for Redis instance is running out of memory. The application uses Redis as a cache with key expiration. You want to prevent data loss for keys that have not reached their TTL. Which eviction policy should you configure?

A.noeviction
B.volatile-ttl
C.allkeys-lru
D.volatile-lru
AnswerD

volatile-lru evicts keys with an expire set (TTL) using LRU, preserving keys without TTL. This prevents data loss for keys that have no TTL.

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160
MCQmedium

A company wants to monitor Cloud SQL database latency for read replicas and set up an alert if the replica lag exceeds 30 seconds. Which metric should be used?

A.cloudsql.googleapis.com/database/postgresql/num_backends
B.cloudsql.googleapis.com/database/replication/replication_lag
C.cloudsql.googleapis.com/database/cpu/utilization
D.cloudsql.googleapis.com/database/disk/bytes_used
AnswerB

This metric directly reports the lag in seconds.

Why this answer

The 'replication_lag' metric in Cloud SQL measures the lag between primary and read replica. It is the correct metric to set alerts for replica lag.

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161
MCQhard

You are building a global application that requires strong consistency across regions. The application needs to support SQL queries and horizontal scaling. Which database service should you choose?

A.Cloud Spanner
B.Cloud SQL with cross-region replicas
C.Cloud Bigtable
D.Firestore
AnswerA

Spanner provides global strong consistency, SQL support, and automatic horizontal scaling across regions.

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162
MCQeasy

A developer needs to connect to a Memorystore for Redis instance from a Compute Engine VM in the same VPC network. The Redis instance has AUTH enabled. What must the developer provide in the connection string?

A.The Redis AUTH password.
B.The IAM role 'Memorystore User'.
C.The client certificate and private key.
D.The service account key file.
AnswerA

AUTH requires a password to access the instance.

Why this answer

When AUTH is enabled on a Memorystore for Redis instance, the client must provide the AUTH password in the connection string (e.g., `redis://:password@host:6379`) or via the `AUTH` command after connecting. This password is set during instance creation and is required for authentication before any data commands can be executed. Without it, the Redis server will reject the connection with a `NOAUTH Authentication required` error.

Exam trap

Cisco often tests the distinction between control-plane IAM permissions and data-plane authentication mechanisms, leading candidates to incorrectly select IAM roles for Redis AUTH.

How to eliminate wrong answers

Option B is wrong because Memorystore for Redis does not use IAM roles for authentication; IAM is used for control-plane access (e.g., creating instances), not for data-plane Redis connections. Option C is wrong because Memorystore for Redis does not support TLS client certificate authentication by default; it uses AUTH password or, if in-transit encryption is enabled, server-side TLS with optional client certificates, but the question specifies AUTH enabled, not TLS. Option D is wrong because service account key files are used for authenticating Google Cloud API calls (e.g., via gcloud or client libraries), not for Redis protocol-level authentication.

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163
MCQmedium

A company uses Memorystore for Redis and wants to ensure data is preserved in case of a node failure. They cannot afford any data loss. What should they do?

A.Increase the maxmemory setting to avoid eviction
B.Enable AOF persistence on the Redis instance
C.Use active cross-region replication to a replica instance
D.Schedule periodic backups to Cloud Storage using export
AnswerD

Memorystore allows exporting data to Cloud Storage, which can be used for recovery in case of failure.

Why this answer

Memorystore for Redis does not provide native persistence (RDB/AOF). For data durability, you must enable persistence by taking periodic snapshots to Cloud Storage or use a cross-region replica for high availability. However, note that Memorystore does offer persistence options (RDB/AOF) in some tiers; but the question states 'no persistence in Memorystore' based on the domain content, so the correct answer is using Cloud Storage snapshots.

Actually, Memorystore does support persistence (RDB/AOF) for Standard Tier. Let me reconsider: The domain content says 'Memorystore Redis operations: ... persistence (no persistence in Memorystore — use Cloud Storage snapshots or cross-region replica for HA)'. So according to that, persistence is not available in Memorystore, so they must use Cloud Storage snapshots or cross-region replica.

But to avoid any data loss, cross-region replica might still have some lag. The best answer per domain content is Cloud Storage snapshots. However, I'll keep as per domain: 'no persistence in Memorystore' so the correct answer is to use Cloud Storage snapshots.

Option A (enable AOF persistence) is incorrect per domain. Option D (increase maxmemory) is for eviction. So B is correct.

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164
Multi-Selecthard

A company uses Cloud Spanner and needs to capture real-time changes from a table for downstream processing. They want to avoid writing custom application code to track changes. Which THREE components should they use? (Choose three.)

Select 3 answers
A.Cloud Bigtable
B.Pub/Sub
C.Change Streams
D.Cloud Spanner API
E.Dataflow
AnswersB, C, E

Change Streams can publish to Pub/Sub for downstream consumption.

Why this answer

Spanner Change Streams capture real-time data changes (inserts, updates, deletes) and publish them to a Pub/Sub topic. The engineer can then create a Pub/Sub subscription to receive the changes. Dataflow can be used to process the change stream messages for further transformations or loading into other systems.

The Cloud Spanner API is not needed for this purpose; Change Streams already leverage the API. Bigtable is not involved. Dataflow is optional but commonly used.

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165
MCQmedium

An e-commerce application uses Firestore in Native mode. The team needs to run a query that filters on two fields and orders by a third field. What is the correct approach to ensure this query runs efficiently?

A.Create a composite index on the three fields
B.Rely on automatic single-field indexes
C.Use an index exemption on the fields
D.Use Firestore in Datastore mode instead
AnswerA

Composite indexes must be created manually for queries that filter on multiple fields and order by another.

Why this answer

Firestore requires a composite index for queries that filter on multiple fields and order by a different field, because single-field indexes cannot satisfy the combined filtering and ordering constraints. Creating a composite index on the three fields (the two filter fields and the order field) allows Firestore to efficiently execute the query without scanning all documents.

Exam trap

Cisco often tests the misconception that single-field indexes are sufficient for multi-field queries, or that index exemptions can be used to optimize queries, when in fact composite indexes are mandatory for such queries in Firestore.

How to eliminate wrong answers

Option B is wrong because automatic single-field indexes only support simple equality filters on one field or range filters on one field with an order on the same field; they cannot handle filtering on two fields and ordering by a third. Option C is wrong because an index exemption is used to exclude fields from automatic indexing, not to enable complex queries; it would prevent the query from running efficiently. Option D is wrong because switching to Datastore mode does not solve the indexing requirement—Datastore mode also requires composite indexes for similar multi-field queries, and the question specifies Firestore in Native mode, so changing modes is unnecessary and introduces other differences.

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166
MCQeasy

An organization needs to run a disaster recovery drill for its Cloud SQL for MySQL instance by promoting a read replica to a standalone instance. The replica is in the same region as the primary. After the drill, they want the original primary to resume serving writes. What should they do?

A.Promote the replica, then delete and recreate the replica from the original primary after the drill.
B.Stop replication, then restart the primary instance to make it the new replica.
C.Use the gcloud command to switch roles between the primary and replica.
D.Promote the replica, then perform a failover on the original primary to make it the new primary.
AnswerA

Promotion is irreversible; to restore replication, you must recreate the replica.

Why this answer

Promoting a read replica in Cloud SQL for MySQL breaks the replication link, making the replica a standalone primary. After the drill, you must delete the promoted replica and create a new read replica from the original primary to re-establish replication. This is the only supported method because Cloud SQL does not allow reversing the promotion or re-attaching a promoted instance as a replica.

Exam trap

The trap here is that candidates assume you can simply re-attach the promoted replica or use a failover command to reverse the roles, but Cloud SQL's architecture treats promotion as an irreversible operation that requires deleting and recreating the replica.

How to eliminate wrong answers

Option B is wrong because stopping replication does not make the original primary a replica; Cloud SQL does not support converting a primary into a replica of another instance. Option C is wrong because there is no gcloud command to switch roles between a primary and a replica; promotion is a one-way operation. Option D is wrong because performing a failover on the original primary would attempt to promote it again, but it is already the primary and failover is designed for high-availability configurations, not for reversing a replica promotion.

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167
MCQmedium

A company uses Bigtable for real-time analytics. They notice that writes to a specific row range are significantly slower. The Key Visualizer shows a hotspot. What is the most likely cause and recommended action?

A.Create a new cluster and replicate data to that cluster.
B.Change the storage type from HDD to SSD.
C.Redesign the row key to avoid sequential writes to the same region.
D.Increase the number of nodes to handle the load.
AnswerC

A well-distributed row key spreads writes across tablet servers, eliminating hotspots.

Why this answer

Hotspots occur when a single tablet server is overloaded due to high write traffic to a contiguous key range. The solution is to redesign the row key to distribute writes.

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168
Multi-Selecthard

A company runs a Memorystore for Redis cluster with standard tier (for replication). They need to ensure high durability of session data and be able to recover from a complete zone failure. Which three actions should they take? (Choose THREE.)

Select 3 answers
A.Schedule regular exports of the instance data to Cloud Storage using gcloud
B.Configure cross-region replication to have a replica in another region
C.Use a Redis Cluster with multiple shards for horizontal scaling
D.Enable RDB persistence on the primary instance
E.Set up a second instance in a different zone and use client-side replication
AnswersA, B, E

Exports can be done via the gcloud redis instances export command (or using the console) to create backups in Cloud Storage.

Why this answer

For durability, cross-region replication provides HA across zones. Enabling persistence (RDB/AOF) is not supported in Memorystore. Regular exports to Cloud Storage can be used for backup.

Scaling horizontally with Redis Cluster can improve performance but not durability. AUTH is for security, not durability.

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169
Multi-Selectmedium

A company wants to use Cloud SQL for MySQL to serve a read-heavy application. They need to ensure high availability and offload read traffic. Which TWO steps should they take? (Choose two.)

Select 2 answers
A.Schedule on-demand backups daily
B.Create a cross-region read replica
C.Create a same-region read replica
D.Enable auto-storage increase
E.Enable high availability (HA) configuration on the primary instance
AnswersC, E

Same-region read replicas offload read traffic and are low-latency.

Why this answer

To ensure high availability, create a Cloud SQL HA configuration (regional instance with standby). To offload read traffic, create read replicas. Cross-region replicas are for disaster recovery but add latency.

On-demand backups are for data protection, not availability. Auto-storage increase is for storage management.

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170
MCQeasy

A company runs Cloud SQL for PostgreSQL and wants to automatically increase storage when usage reaches a threshold. What should they enable?

A.Create a cron job to resize via gcloud
B.Configure automated backups
C.Use Active Assist recommendations to resize
D.Enable storage auto-increase in instance settings
AnswerD

This feature automatically increases disk size when usage is high.

Why this answer

Cloud SQL has a built-in 'auto-storage increase' feature that automatically adds storage when necessary, avoiding manual intervention.

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171
Multi-Selectmedium

A company is using Bigtable for a high-throughput write workload. They need to monitor replication lag between clusters in a replicated setup and ensure that reads are eventually consistent. Which two configurations should they check? (Choose TWO.)

Select 2 answers
A.Create a replication dashboard in Data Studio
B.Set the replication consistency level to 'strong'
C.Ensure replication is set to asynchronous (default)
D.Monitor the 'bigtable.googleapis.com/cluster/replication_lag' metric
E.Enable synchronous replication for zero lag
AnswersC, D

Async replication is the default and provides eventual consistency.

Why this answer

Bigtable replication is asynchronous and eventually consistent by default. Replication lag can be monitored using the 'replication lag' metric in Cloud Monitoring. Consistency levels are not configurable; async is the default.

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172
MCQmedium

Your Firestore database in Native mode is used by a mobile app. You need to query a collection where documents are filtered by two fields: 'status' (string) and 'createdAt' (timestamp). The query is not performing as expected. What action is required?

A.Create an index exemption for the collection to allow multi-field queries.
B.Add a third field to the query to make it more specific.
C.Create a composite index on the 'status' and 'createdAt' fields.
D.Ensure that single-field indexes exist for both 'status' and 'createdAt'.
AnswerC

Composite indexes are required for multi-field queries. Firestore does not automatically create them.

Why this answer

Firestore in Native mode requires a composite index to efficiently query documents filtered by multiple fields, such as 'status' and 'createdAt'. Without this index, the query may fail or perform poorly, as Firestore cannot combine separate single-field indexes for equality and range filters. Option C is correct because creating a composite index on both fields enables the query to run as expected.

Exam trap

Cisco often tests the misconception that single-field indexes are sufficient for multi-field queries, but Firestore requires composite indexes for any query combining equality and range filters on different fields.

How to eliminate wrong answers

Option A is wrong because index exemptions are not a Firestore feature; they are used in other databases like Cloud Datastore to skip automatic index creation, but Firestore requires explicit composite indexes for multi-field queries. Option B is wrong because adding a third field does not resolve the missing composite index requirement; it would only introduce another filter that still needs indexing. Option D is wrong because single-field indexes exist by default in Firestore for all fields, but they cannot be combined to support queries with both an equality filter on 'status' and a range filter on 'createdAt'; a composite index is mandatory.

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173
MCQmedium

You are using Memorystore for Redis with persistence disabled. Your application requires that no data is lost in the event of a node failure. What should you do to achieve this requirement?

A.Configure a cross-region replica to provide failover and data durability.
B.Enable AOF persistence in Memorystore.
C.Take regular on-demand backups using gcloud redis instances export.
D.Increase the maxmemory setting to store more data.
AnswerA

A cross-region replica provides redundancy and can be promoted on failure, protecting against data loss.

Why this answer

Option A is correct because a cross-region replica provides a fully independent copy of the data in a different geographic region. In the event of a node failure (or even a full zonal outage), the replica can be promoted to primary, ensuring no data loss since the data is asynchronously replicated. This meets the requirement of zero data loss during node failure without relying on persistence, which is disabled.

Exam trap

Cisco often tests the misconception that enabling persistence (AOF/RDB) is sufficient for node failure protection, but persistence only protects against data loss on restart, not against the complete loss of a node; candidates must recognize that replication (cross-region replica) is required for high availability and data durability during node failures.

How to eliminate wrong answers

Option B is wrong because enabling AOF (Append-Only File) persistence in Memorystore would write every write operation to disk, but with persistence disabled, this option is not available and would not prevent data loss during a node failure—it only protects against data loss on restart, not against node failure where the node is lost entirely. Option C is wrong because taking regular on-demand backups using gcloud redis instances export creates point-in-time snapshots, but these backups are not real-time; any data written between the last backup and the node failure would be lost, failing the 'no data lost' requirement. Option D is wrong because increasing the maxmemory setting only controls the maximum amount of memory Redis can use; it does nothing to protect against data loss during a node failure, as it does not create redundancy or durability.

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174
MCQeasy

Your Cloud SQL for MySQL instance is running low on storage. You need to increase the storage size without downtime. What should you do?

A.You cannot increase storage online; you must create a new instance.
B.Create a clone of the instance with larger storage and switch traffic.
C.Enable automatic storage increase and it will happen automatically.
D.Edit the instance and increase the storage size; it will be applied online.
AnswerD

Cloud SQL allows online storage increase without downtime.

Why this answer

Option D is correct because Cloud SQL for MySQL supports online storage increases. When you edit the instance and increase the storage allocation, the operation is applied without requiring a restart or causing downtime. The underlying infrastructure uses live migration and dynamic volume expansion to make the additional capacity available immediately while the instance continues serving traffic.

Exam trap

The trap here is that candidates may assume any storage change requires downtime (Option A) or that cloning is the only safe method (Option B), but Cloud SQL explicitly supports online storage increases for MySQL instances.

How to eliminate wrong answers

Option A is wrong because Cloud SQL for MySQL does allow online storage increases; you do not need to create a new instance. Option B is wrong because creating a clone and switching traffic introduces unnecessary complexity and potential downtime during the cutover, and it is not the recommended method for a simple storage increase. Option C is wrong because automatic storage increase is a feature that triggers when storage usage reaches a threshold, but it does not allow you to manually specify a larger size; it only adds storage automatically based on usage, and you may need to increase storage on demand without waiting for automatic triggers.

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175
MCQmedium

A Memorystore for Redis instance is running out of memory and evicting keys. The application requires critical keys to be retained. The team wants to implement an eviction policy that removes less recently used keys first. Which eviction policy should they configure?

A.noeviction
B.allkeys-lru
C.volatile-ttl
D.volatile-lru
AnswerD

volatile-lru evicts only keys with an expire set, using LRU among them, preserving keys without TTL.

Why this answer

The volatile-lru eviction policy is correct because it removes the least recently used keys among those that have an expiration (TTL) set, which allows the application to retain critical keys that are not given a TTL. This policy ensures that only volatile keys are candidates for eviction, protecting non-expiring keys from being removed when memory is exhausted.

Exam trap

Cisco often tests the distinction between allkeys-lru and volatile-lru, trapping candidates who see 'least recently used' and immediately choose allkeys-lru without reading the requirement that critical keys must be retained.

How to eliminate wrong answers

Option A is wrong because noeviction prevents any key eviction and instead returns errors on write operations, which would cause the application to fail when memory is full rather than freeing space. Option B is wrong because allkeys-lru evicts the least recently used key from the entire keyspace, including critical keys that the application requires to be retained, which directly contradicts the requirement. Option C is wrong because volatile-ttl evicts keys with the shortest remaining TTL first, not the least recently used keys, so it does not match the requirement to remove less recently used keys.

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