What is a distributed system?

A distributed system is a collection of independent computers that appears to its users as a single coherent system, working together to solve a common problem or provide a unified service.

What does the CAP theorem state about distributed systems?

The CAP theorem states that it is impossible for a distributed system to simultaneously provide more than two out of the following three guarantees:

• Consistency: All nodes see the same data at the same time
• Availability: Every request receives a response, without guarantee that it contains the most recent version of the information
• Partition tolerance: The system continues to operate despite arbitrary partitioning due to network failures

Explain the concept of eventual consistency in distributed systems.

Eventual consistency is a consistency model used in distributed computing to achieve high availability. It guarantees that, if no new updates are made to a given data item, eventually all accesses to that item will return the last updated value.

What is sharding in the context of distributed databases?

Sharding is a database partitioning technique where large databases are divided into smaller, faster, more easily managed parts called shards. Each shard is held on a separate database server instance, to spread load and improve performance.

Define consensus algorithms and provide an example.

Consensus algorithms are protocols for a group of nodes to agree on a single data value, even in the presence of failures. They are crucial for maintaining consistency in distributed systems.

Example: Paxos, Raft

What is load balancing and why is it important in distributed systems?

Load balancing is the process of distributing network traffic across multiple servers to ensure no single server bears too much demand. It is important because it:

• Improves responsiveness and availability of applications
• Prevents any single server from becoming a point of failure
• Helps handle increases in traffic

Explain the concept and purpose of a distributed hash table (DHT).

A distributed hash table (DHT) is a decentralized distributed system that provides a lookup service similar to a hash table. Key-value pairs are stored in the DHT, and any participating node can efficiently retrieve the value associated with a given key.

DHTs form the foundation for more complex distributed systems like peer-to-peer file sharing networks and content delivery networks.