Data replication strategies in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the primary replication type used for high availability.

HLD

ReplicationType = "[1]"  # Commonly used for synchronous data copying

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

AAsynchronous

BEventual

CSynchronous

DSnapshot

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing asynchronous which delays data copying.

Synchronous replication ensures data is copied to replicas immediately, providing high availability.

2fill in blank

medium

Complete the code to select the replication strategy that allows replicas to lag behind the primary.

HLD

ReplicationStrategy = "[1]"  # Replicas update after some delay

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

AAsynchronous

BQuorum-based

CSynchronous

DMulti-master

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing with synchronous replication which waits for confirmation.

Asynchronous replication allows replicas to lag, improving performance but risking stale reads.

3fill in blank

hard

Fix the error in the replication mode assignment to correctly represent multi-master replication.

HLD

replication_mode = "[1]"  # Allows multiple nodes to accept writes

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

AMulti-master

BSingle-master

CPrimary-secondary

DRead-only

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing single-master which restricts writes to one node.

Multi-master replication allows multiple nodes to accept writes simultaneously, improving availability.

4fill in blank

hard

Fill both blanks to complete the code for a quorum-based replication read and write strategy.

HLD

write_quorum = "[1]"  # Minimum nodes to confirm write
read_quorum = "[2]"   # Minimum nodes to confirm read

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

Amajority

Ball

Cone

Dnone

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'all' which is stricter and less available.

Quorum-based replication requires a majority of nodes to confirm reads and writes to ensure consistency.

5fill in blank

hard

Fill all three blanks to complete the code for a replication setup with primary, secondary, and failover nodes.

HLD

primary_node = "[1]"
secondary_node = "[2]"
failover_node = "[3]"

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

Aaccepts writes

Breplicates data

Ctakes over if primary fails

Dmonitors health

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing failover with monitoring role.

The primary node accepts writes, the secondary replicates data, and the failover takes over if the primary fails.

Practice

1. Which data replication strategy ensures that all copies of data are updated at the same time before confirming a write operation?

easy

A. Synchronous replication

B. Asynchronous replication

C. Master-slave replication

D. Multi-master replication

Solution

1. Step 1: Understand synchronous replication

   Synchronous replication waits for all copies to confirm the write before completing the operation.

2. Step 2: Compare with other strategies

   Asynchronous replication does not wait, master-slave and multi-master describe topology, not timing.

3. Final Answer:

   Synchronous replication -> Option A

4. Quick Check:

   Strong consistency = Synchronous replication [OK]

Hint: Strong consistency means waiting for all copies to update [OK]

Common Mistakes:

• Confusing asynchronous with synchronous replication
• Mixing replication timing with replication topology
• Assuming master-slave means synchronous

2. Which of the following is the correct description of asynchronous replication?

easy

A. Replicas confirm the data before the primary confirms the write

B. Data is copied to replicas without waiting for confirmation from them

C. Data is copied simultaneously to all replicas with confirmation

D. Data is copied to replicas before the primary confirms the write

Solution

1. Step 1: Define asynchronous replication

   It copies data to replicas but does not wait for their confirmation before confirming the write.

2. Step 2: Eliminate other options

   Replicas confirm the data before the primary confirms the write requires replica confirmation before primary ack (synchronous); B copies before primary ack (incorrect); C describes synchronous behavior.

3. Final Answer:

   Data is copied to replicas without waiting for confirmation from them -> Option B

4. Quick Check:

   Asynchronous = no wait for replica confirmation [OK]

Hint: Asynchronous means no waiting for replicas to confirm [OK]

Common Mistakes:

• Thinking asynchronous waits for replicas
• Confusing timing of data copy
• Mixing synchronous and asynchronous definitions

3. Consider a system using master-slave replication. If the master receives a write request, what happens next?

medium

A. The write is applied simultaneously to master and slaves synchronously

B. The write is applied to all slaves first, then to the master

C. The write is only applied to slaves, not the master

D. The write is applied to the master and then asynchronously copied to slaves

Solution

1. Step 1: Understand master-slave replication flow

   Writes go to the master first, then are copied to slaves, usually asynchronously.

2. Step 2: Check other options

   Slaves do not receive writes first or alone; synchronous writes to all are not typical in master-slave.

3. Final Answer:

   The write is applied to the master and then asynchronously copied to slaves -> Option D

4. Quick Check:

   Master handles writes first in master-slave [OK]

Hint: Master handles writes first, slaves get updates later [OK]

Common Mistakes:

• Assuming slaves can accept writes first
• Confusing synchronous with asynchronous replication
• Thinking slaves are independent masters

4. A system using multi-master replication faces conflicts when two masters update the same data simultaneously. What is a common way to fix this issue?

medium

A. Switch to asynchronous replication only

B. Disable writes on all but one master

C. Use conflict resolution strategies like timestamps or version vectors

D. Remove all replicas and use a single database

Solution

1. Step 1: Identify conflict in multi-master replication

   Simultaneous writes cause conflicts that need resolution strategies.

2. Step 2: Evaluate conflict resolution methods

   Timestamps or version vectors help decide which write wins or how to merge.

3. Final Answer:

   Use conflict resolution strategies like timestamps or version vectors -> Option C

4. Quick Check:

   Conflict resolution = timestamps/version vectors [OK]

Hint: Resolve conflicts with timestamps or version vectors [OK]

Common Mistakes:

• Disabling multi-master writes defeats purpose
• Thinking asynchronous replication solves conflicts
• Removing replicas is impractical

5. You are designing a global application with users worldwide needing fast reads and writes. Which replication strategy best fits this use case?

hard

A. Multi-master replication with conflict resolution

B. Master-slave replication with synchronous writes

C. Single master with asynchronous replication

D. No replication, single database instance

Solution

1. Step 1: Analyze global user needs

   Users worldwide require fast reads and writes from multiple locations.

2. Step 2: Match replication strategy

   Multi-master allows writes at multiple locations with conflict resolution, improving speed and availability.

3. Step 3: Eliminate other options

   Master-slave with synchronous writes is slow globally; single master limits write locations; no replication is slow and risky.

4. Final Answer:

   Multi-master replication with conflict resolution -> Option A

5. Quick Check:

   Global fast writes = multi-master + conflict resolution [OK]

Hint: Global writes need multi-master with conflict handling [OK]

Common Mistakes:

• Choosing synchronous master-slave for global writes
• Ignoring conflict resolution in multi-master
• Using single master limits write speed globally