Consistent hashing in HLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is consistent hashing?

Consistent hashing is a technique to distribute data across multiple servers so that when servers are added or removed, only a small portion of data needs to be moved. It helps systems scale smoothly.

intermediate

Why is consistent hashing better than simple modulo hashing for distributed systems?

Simple modulo hashing moves almost all data when the number of servers changes. Consistent hashing moves only a small part, reducing data reshuffling and downtime.

beginner

What is a hash ring in consistent hashing?

A hash ring is a circular space where both servers and data keys are placed using a hash function. Data is assigned to the next server clockwise on the ring.

intermediate

How do virtual nodes improve consistent hashing?

Virtual nodes are multiple points per server on the hash ring. They help balance load better by spreading data more evenly across servers.

beginner

What happens when a server is removed in consistent hashing?

Only the data assigned to that server moves to the next server on the ring. Other data stays on their servers, minimizing data movement.

What does consistent hashing minimize when servers change?

A Number of servers

B Amount of data moved

C Hash function complexity

D Network latency

Consistent hashing minimizes the amount of data that needs to be moved when servers are added or removed.

In consistent hashing, where is data assigned on the hash ring?

A To the server at the next clockwise position

B To the server at the previous counterclockwise position

C To a random server

D To all servers equally

Data is assigned to the server at the next clockwise position on the hash ring.

What is the purpose of virtual nodes in consistent hashing?

A To increase hash collisions

B To encrypt data

C To reduce the number of servers

D To improve load balancing

Virtual nodes help distribute data more evenly, improving load balancing.

Which problem does consistent hashing solve in distributed systems?

A User authentication

B Slow database queries

C Data reshuffling on server changes

D Network packet loss

Consistent hashing reduces data reshuffling when servers are added or removed.

What shape is used to visualize consistent hashing?

A Circle (hash ring)

B Square grid

C Tree diagram

D Line graph

Consistent hashing is visualized as a circle called a hash ring.

Explain how consistent hashing helps when adding or removing servers in a distributed system.

Think about how data is distributed and what happens when servers change.

Describe the role of virtual nodes in consistent hashing and why they are useful.

Consider how virtual nodes affect data balance across servers.