Database replication (master-slave) in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary role of the master in a master-slave database replication setup?

In a master-slave replication system, what is the main responsibility of the master database?

A To handle all write operations and propagate changes to slaves

B To serve read requests only without accepting writes

C To synchronize data from slaves to itself

D To act as a backup server without processing any requests

💡 Hint

Think about which database handles data changes first.

The master database is responsible for processing all write operations and then sending those changes to the slave databases to keep them updated.

❓ Architecture

intermediate

Which component ensures data consistency between master and slaves in replication?

In a master-slave replication architecture, which mechanism is primarily used to keep slave databases consistent with the master?

A Manual synchronization by database administrators

B Periodic full database snapshots sent to slaves

C Slaves independently polling the master for changes

D Binary log shipping from master to slaves

💡 Hint

Consider how changes are recorded and sent continuously.

The master records all changes in a binary log and ships these logs to slaves, which replay them to stay consistent.

❓ scaling

advanced

How does master-slave replication improve read scalability?

In a system using master-slave replication, how is read scalability typically improved?

A By increasing the number of write operations on the master

B By making slaves handle write requests to reduce master load

C By directing read requests to multiple slave databases to distribute load

D By disabling replication during peak read times

💡 Hint

Think about how slaves can help with read requests.

Slaves can serve read requests, allowing the system to handle more reads by spreading the load across multiple servers.

❓ tradeoff

advanced

What is a common tradeoff when using asynchronous master-slave replication?

Choosing asynchronous replication between master and slaves often leads to which tradeoff?

A Potential data loss on master failure due to lag in replication

B Slower write performance on the master due to waiting for slaves

C Slaves becoming write masters automatically

D Increased network traffic from slaves to master

💡 Hint

Consider what happens if the master crashes before slaves catch up.

Asynchronous replication means slaves may lag behind the master, risking data loss if the master fails before changes reach slaves.

❓ estimation

expert

Estimate the maximum number of slaves supported given network bandwidth constraints

A master database generates 100 MB of binary log data per minute. Each slave requires a dedicated network connection with 10 MB/min bandwidth to receive replication data without lag. What is the maximum number of slaves that can be supported without replication delay?

A 1 slave

B 10 slaves

C 50 slaves

D 100 slaves

💡 Hint

Divide total data generated by bandwidth per slave.

The master produces 100 MB/min. Each slave needs 10 MB/min. So, 100 / 10 = 10 slaves can be supported without lag.