Read replicas in GCP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a read replica instance in Cloud SQL.

GCP

gcloud sql instances create replica-instance --master-instance-name=[1] --region=us-central1

Drag options to blanks, or click blank then click option'

Areplica-instance

Bprimary-instance

Cbackup-instance

Dmain-instance

Attempts:

3 left

💡 Hint

Common Mistakes

Using the replica instance name instead of the primary instance name.

Confusing backup instances with master instances.

The --master-instance-name flag specifies the primary instance to replicate from.

2fill in blank

medium

Complete the code to enable replication on the primary Cloud SQL instance.

GCP

gcloud sql instances patch primary-instance --[1]=ON

Drag options to blanks, or click blank then click option'

Abackup

Bmaintenance

Cbin-log-enabled

Dfailover

Attempts:

3 left

💡 Hint

Common Mistakes

Enabling backup instead of replication.

Using maintenance or failover flags incorrectly.

Enabling bin-log-enabled on the primary instance allows read replicas to sync data.

3fill in blank

hard

Fix the error in the command to list read replicas of a Cloud SQL instance.

GCP

gcloud sql instances list --filter='[1]:REPLICA'

Drag options to blanks, or click blank then click option'

Ainstance

Brole

Creplica

DINSTANCE_TYPE

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'REPLICA' as a filter key instead of a value.

Using 'role' or 'instance' which are not valid filter keys here.

The filter key INSTANCE_TYPE is used to specify instance types like 'REPLICA'.

4fill in blank

hard

Fill both blanks to configure a read replica with a specific machine type and storage size.

GCP

gcloud sql instances create replica-instance --master-instance-name=primary-instance --tier=[1] --storage-size=[2]

Drag options to blanks, or click blank then click option'

Adb-custom-2-3840

Bdb-f1-micro

C20GB

D10GB

Attempts:

3 left

💡 Hint

Common Mistakes

Using a very small machine type that is not recommended for replicas.

Specifying storage size without units.

The --tier flag sets the machine type, and --storage-size sets the disk size for the replica.

5fill in blank

hard

Fill all three blanks to create a read replica with a specific region, activation policy, and database version.

GCP

gcloud sql instances create replica-instance --master-instance-name=primary-instance --region=[1] --activation-policy=[2] --database-version=[3]

Drag options to blanks, or click blank then click option'

Aus-east1

Balways

CPOSTGRES_14

Dus-west1

Attempts:

3 left

💡 Hint

Common Mistakes

Using an invalid region name.

Setting activation policy to 'never' which disables the instance.

Choosing a database version that does not match the primary.

The --region flag sets the location, --activation-policy controls instance start behavior, and --database-version specifies the database engine version.

Practice

1.

What is the main purpose of a read replica in Google Cloud SQL?

easy

A. To copy the main database and handle read requests to reduce load

B. To store backups of the database for disaster recovery

C. To serve as a primary database for write operations

D. To encrypt data stored in the database

Solution

1. Step 1: Understand the role of read replicas

   Read replicas copy data from the main database and serve read requests to reduce load on the primary instance.

2. Step 2: Differentiate from other database roles

   Backups and encryption are different features; read replicas do not handle writes.

3. Final Answer:

   To copy the main database and handle read requests to reduce load -> Option A

4. Quick Check:

   Read replica purpose = reduce load by handling reads [OK]

Hint: Read replicas handle reads to reduce main database load [OK]

Common Mistakes:

• Confusing read replicas with backups
• Thinking read replicas handle writes
• Assuming read replicas encrypt data

2.

Which gcloud command correctly creates a read replica named replica-instance of a master instance called master-instance?

easy

A. gcloud sql instances create replica-instance --master-instance-name=master-instance

B. gcloud sql instances create replica-instance --replica-of=master-instance

C. gcloud sql replicas create replica-instance --master=master-instance

D. gcloud sql create instance replica-instance --master=master-instance

Solution

1. Step 1: Recall the correct command syntax

   The correct command to create a read replica uses gcloud sql instances create with the flag --master-instance-name.

2. Step 2: Verify option correctness

   gcloud sql instances create replica-instance --master-instance-name=master-instance matches the correct syntax exactly; other options use incorrect flags or commands.

3. Final Answer:

   gcloud sql instances create replica-instance --master-instance-name=master-instance -> Option A

4. Quick Check:

   Correct flag for read replica creation = --master-instance-name [OK]

Hint: Use --master-instance-name flag with gcloud sql instances create [OK]

Common Mistakes:

• Using incorrect flags like --replica-of
• Using wrong gcloud subcommands
• Mixing up command order or syntax

3.

Consider this command output snippet after creating a read replica:

NAME              REGION       MASTER_INSTANCE
replica-instance  us-central1  master-instance

What does this output indicate?

medium

A. The master-instance is a read replica of replica-instance

B. The replica-instance is the primary database in us-central1 region

C. The replica-instance is a read replica of master-instance in us-central1 region

D. The replica-instance is a backup stored in us-central1

Solution

1. Step 1: Analyze the output columns

   The output shows the replica name, its region, and the master instance it replicates.

2. Step 2: Interpret the relationship

   Since replica-instance lists master-instance as its master, it is a read replica of that master in the specified region.

3. Final Answer:

   The replica-instance is a read replica of master-instance in us-central1 region -> Option C

4. Quick Check:

   Replica points to master-instance = read replica relationship [OK]

Hint: Master instance listed means replica points to it for reads [OK]

Common Mistakes:

• Confusing replica as primary
• Thinking master is replica
• Assuming backup instead of replica

4.

You tried to create a read replica with this command:

gcloud sql instances create replica1 --master=master1

But it failed. What is the likely cause?

medium

A. You must create the replica before the master instance

B. The replica name cannot contain numbers

C. The master instance must be in a different region

D. The flag --master is incorrect; should use --master-instance-name

Solution

1. Step 1: Check the command flags

   The correct flag to specify the master instance is --master-instance-name, not --master.

2. Step 2: Validate other options

   Replica names can contain numbers; master and replica can be in same region; master must exist before replica.

3. Final Answer:

   The flag --master is incorrect; should use --master-instance-name -> Option D

4. Quick Check:

   Correct flag for master instance = --master-instance-name [OK]

Hint: Use exact flag --master-instance-name to link replica to master [OK]

Common Mistakes:

• Using wrong flag --master
• Thinking replica name rules are stricter
• Assuming region mismatch causes failure

5.

You have a master instance handling both reads and writes. To improve read performance globally, you want to create two read replicas in different regions. Which approach is best?

1. Create two read replicas using gcloud sql instances create with --master-instance-name for each region.
2. Configure your application to send read queries to replicas and write queries to the master.
3. Ensure replicas are in regions close to your users for low latency.

What is the correct reasoning behind this approach?

hard

A. Read replicas automatically handle writes to reduce master load

B. Read replicas reduce load on master and improve read latency by being regionally closer to users

C. Creating replicas in multiple regions duplicates writes to all replicas instantly

D. Replicas replace the master for all database operations

Solution

1. Step 1: Understand read replica benefits

   Read replicas copy data from the master and serve read requests, reducing load on the master.

2. Step 2: Consider regional placement and query routing

   Placing replicas near users lowers latency; routing reads to replicas and writes to master optimizes performance.

3. Step 3: Clarify write behavior

   Replicas do not handle writes; writes go only to the master and replicate asynchronously.

4. Final Answer:

   Read replicas reduce load on master and improve read latency by being regionally closer to users -> Option B

5. Quick Check:

   Replicas improve read speed and reduce master load [OK]

Hint: Replicas serve reads near users; writes stay on master [OK]

Common Mistakes:

• Assuming replicas handle writes
• Thinking replicas instantly sync writes synchronously
• Believing replicas replace the master