Consensus Algorithms: Achieving Agreement in Distributed Systems

Question 1

Which of the following is not a consensus algorithm used in distributed systems?

Accepted Answer

Blockchain

Answer

Primary-based

Answer

Quorum-based

Answer

Paxos

Question 2

Which of the following is a fundamental property of consensus algorithms?

Accepted Answer

They guarantee that all non-faulty processes agree on the same value.

Answer

They are always highly efficient.

Answer

They can tolerate any number of failures.

Answer

They are straightforward to implement.

Question 3

What is a key benefit of employing a consensus algorithm in a distributed system?

Accepted Answer

Enhanced fault tolerance

Answer

Improved performance

Answer

Reduced complexity

Answer

Enhanced security

Question 4

What is a fundamental difference between the Paxos and Raft consensus algorithms?

Accepted Answer

Paxos uses a leader-based approach, while Raft is leaderless.

Answer

Paxos employs a two-phase commit protocol, while Raft uses a three-phase commit protocol.

Answer

Paxos is more efficient than Raft.

Answer

Raft is more fault-tolerant than Paxos.

Question 5

Which properties are essential for consensus algorithms in distributed systems?

Accepted Answer

Safety, Liveness, and Agreement

Answer

Validity and Responsiveness

Answer

Fairness and Scalability

Answer

Atomicity and Isolation

Question 6

In leader-based consensus algorithms, what is the primary role of leaders?

Accepted Answer

Facilitating communication and decision-making among participants

Answer

Preventing deadlocks

Answer

Enhancing algorithm performance

Answer

Being dispensable for consensus algorithms

Question 7

In a blockchain network, what is the primary function of consensus algorithms?

Accepted Answer

To ensure agreement on the order of transactions

Answer

To encrypt data transmissions between nodes

Answer

To generate new blocks to add to the blockchain

Answer

To manage access permissions for different users

Question 8

Which type of consensus algorithm is specifically designed to tolerate Byzantine faults?

Accepted Answer

PBFT (Practical Byzantine Fault Tolerance)

Answer

Raft

Answer

Paxos

Answer

Multi-Paxos

Question 9

What is a fundamental distinction between the Paxos and Raft consensus algorithms?

Accepted Answer

Paxos employs a two-phase commit protocol while Raft adopts a leader-follower approach.

Answer

Paxos operates synchronously while Raft is asynchronous.

Answer

Paxos is fault-tolerant while Raft is not.

Question 10

Which of the following is a practical application where consensus algorithms are commonly employed?

Accepted Answer

Maintaining data consistency in a distributed database system.

Answer

Processing images

Answer

Browsing the internet

Question 11

Which aspect presents a significant challenge during the design of consensus algorithms?

Accepted Answer

Effectively handling network delays and failures.

Answer

Ensuring complete data privacy in all scenarios.

Answer

Optimizing algorithm performance for maximum efficiency.

Answer

Providing real-time updates without any delays.

Question 12

Which characteristic defines a crash-tolerant system?

Accepted Answer

Processes may fail by abruptly crashing but do not exhibit arbitrary behavior.

Answer

Processes are guaranteed to operate flawlessly at all times.

Answer

Processes can fail either by crashing or behaving unpredictably.

Question 13

Which of the following is a fundamental property of a consensus algorithm?

Accepted Answer

Agreement

Answer

User-friendliness

Answer

Speed

Answer

Efficiency

Question 14

In the Raft consensus algorithm, which role is responsible for maintaining the current state of the system?

Accepted Answer

Leader

Answer

Observer

Answer

Candidate

Answer

Follower

Question 15

Which of the following consensus algorithms is known for its use in large-scale distributed systems, such as Kubernetes?

Accepted Answer

etcd

Answer

Practical Byzantine Fault Tolerance

Answer

Viewstamped Replication

Answer

ZAB

Question 16

Which type of consensus algorithm is designed to handle malicious participants who may deviate from the protocol?

Accepted Answer

Byzantine Fault Tolerance (BFT)

Answer

Probabilistic Consensus

Answer

Majority Voting

Answer

Leader-based Consensus

Question 17

What is the purpose of a quorum in a consensus algorithm?

Accepted Answer

To ensure that a sufficient number of nodes participate in the decision-making process

Answer

To prevent deadlocks

Answer

To speed up the consensus process significantly

Question 18

What is the key difference between a strong consensus algorithm and a weak consensus algorithm?

Accepted Answer

Strong consensus guarantees that all nodes agree on the same value, while weak consensus allows for some nodes to have different values.

Answer

Strong consensus is faster than weak consensus

Question 19

Which of the following techniques is commonly employed to improve the fault tolerance of consensus algorithms?

Accepted Answer

Replication

Answer

Encryption

Answer

Load balancing

Answer

Error correction codes

Question 20

How does network latency impact the performance of consensus algorithms?

Accepted Answer

Increased latency can slow down the consensus process and reduce throughput

Answer

Latency has no impact on consensus algorithms

Answer

Latency can improve the performance of consensus algorithms

Question 21

Which of the following research areas is actively exploring innovative approaches to consensus algorithms?

Accepted Answer

Blockchain technology

Answer

Cloud computing

Answer

Artificial intelligence

Answer

Software engineering

Question 22

Which of the following is NOT a fundamental property of a consensus algorithm?

Accepted Answer

Efficiency

Answer

Safety

Answer

Agreement

Answer

Liveness

Question 23

Which consensus algorithm is known for employing a rotating coordinator to manage the consensus process?

Accepted Answer

Raft

Answer

ZAB

Answer

Paxos

Question 24

What is the primary function of a quorum in a consensus algorithm?

Accepted Answer

To ensure that a sufficient number of nodes participate in the consensus process, preventing a single node from controlling the outcome.

Answer

To isolate single-node failures from disrupting the consensus process.

Answer

To expedite the consensus process by reducing the number of participating nodes.

Question 25

What is a key benefit of using a consensus algorithm in distributed systems?

Accepted Answer

Guarantees that all nodes in the system agree on the same value or state, even in the presence of failures.

Answer

Simplifies system design by eliminating the need for a centralized authority.

Answer

Reduces the risk of data loss in the event of a node failure.

Answer

Improves performance by reducing network traffic.

Question 26

What is the fundamental difference between a synchronous and an asynchronous consensus algorithm?

Accepted Answer

Synchronous algorithms assume reliable and timely communication between nodes, while asynchronous algorithms operate without such guarantees.

Answer

Synchronous algorithms require a majority of nodes to be active, while asynchronous algorithms do not.

Answer

Synchronous algorithms are consistently faster than asynchronous algorithms.

Question 27

What is the primary role of a leader in a consensus algorithm?

Accepted Answer

To coordinate the consensus process among nodes and propose values for agreement.

Answer

To store the agreed-upon value for the system.

Answer

To broadcast messages to all other nodes in the system.

Question 28

What does the FLP Impossibility Result fundamentally state about consensus algorithms?

Accepted Answer

It is impossible to design a deterministic consensus algorithm that guarantees both fault tolerance and liveness, meaning it can always reach a decision in the presence of failures.

Answer

It is impossible to design a consensus algorithm that can tolerate more than 50% of nodes failing.

Answer

It is impossible to design a consensus algorithm that simultaneously achieves both safety, ensuring no incorrect decisions, and efficiency, in terms of speed.

Question 29

Which of the following is NOT a characteristic of a consensus algorithm?

Accepted Answer

Guaranteed termination within a fixed timeframe.

Answer

Fault tolerance.

Answer

Agreement on a common value.

Answer

Resistance to Byzantine failures.

Question 30

In the context of consensus algorithms, what does "Byzantine Fault Tolerance" refer to?

Accepted Answer

The ability to reach consensus even when some nodes are behaving maliciously.

Answer

The ability to tolerate node crashes.

Answer

The ability to handle network partitions.

Question 31

Which of these consensus algorithms is known for its simplicity and efficiency, but is susceptible to malicious nodes?

Accepted Answer

Paxos.

Answer

Viewstamped Replication.

Answer

Two-Phase Commit.

Answer

Raft.

Question 32

In the context of distributed systems, what is the primary purpose of a consensus algorithm?

Accepted Answer

To ensure all nodes in the system agree on a single, shared value.

Answer

To manage network traffic and prevent congestion.

Answer

To facilitate efficient data distribution across nodes.

Question 33

A distributed system is attempting to reach consensus on the value of a shared variable. Node A proposes value '10', Node B proposes '15', and Node C proposes '10'. Which value will be chosen if the system uses a majority-based consensus algorithm?

Accepted Answer

10

Answer

None, the system will deadlock.

Answer

12.5

Answer

15

Question 34

What is the main advantage of using a leader-based consensus algorithm like Raft over a leaderless approach like Paxos?

Accepted Answer

Simplified implementation and reduced complexity.

Answer

Better scalability in large distributed systems.

Answer

Higher fault tolerance in the presence of network partitions.

Answer

Faster consensus reaching due to centralized decision making.

Question 35

Which of these scenarios would be best suited for using a consensus algorithm like Paxos or Raft?

Accepted Answer

A distributed database system where data consistency is paramount.

Answer

A peer-to-peer file sharing network.

Answer

A system for managing email notifications.

Question 36

What is a common challenge faced when implementing consensus algorithms in real-world distributed systems?

Accepted Answer

Handling network latency and unreliable communication channels.

Answer

Ensuring data security and preventing unauthorized access.

Answer

Managing large amounts of data stored across the nodes.

Question 37

In the context of consensus algorithms, what is a 'round' typically associated with?

Accepted Answer

A series of communication exchanges between nodes to reach agreement.

Answer

A single node's attempt to propose a value.

Answer

A specific phase of the algorithm, like a commit phase.

Question 38

A distributed system using a consensus algorithm experiences a network partition. Which of the following is MOST likely to occur?

Accepted Answer

The system may be unable to reach consensus until the network partition is resolved.

Answer

Nodes in the partitioned group will simply continue processing data independently.

Answer

The system will automatically switch to a different consensus algorithm.

Question 39

Which of the following is NOT a key property of a consensus algorithm?

Accepted Answer

Determinism

Answer

Agreement

Answer

Fault-tolerance

Answer

Validity

Question 40

In a distributed system with Byzantine faults, what is the maximum number of faulty processes that a consensus algorithm can tolerate?

Accepted Answer

f < n/3

Answer

f < n - 1

Answer

f < n/2

Answer

f < n

Question 41

Which consensus algorithm is known for its simplicity and efficiency, but is vulnerable to malicious actors in the presence of Byzantine faults?

Accepted Answer

Paxos

Answer

Two-Phase Commit

Answer

Raft

Answer

Byzantine Fault Tolerant Consensus

Question 42

In a consensus algorithm, what is the purpose of a leader?

Accepted Answer

To coordinate the decision-making process among nodes

Answer

To prevent any node from making decisions

Answer

To handle all data storage and retrieval

Question 43

Which of the following scenarios would NOT be a suitable application for a consensus algorithm?

Accepted Answer

Managing user accounts in a single-server application

Answer

Maintaining a distributed database across multiple data centers

Answer

Coordinating transactions in a blockchain network

Question 44

The process of ensuring that all nodes in a distributed system have the same view of the system's state is called:

Accepted Answer

State Machine Replication

Answer

Byzantine Fault Tolerance

Answer

Leader Election

Answer

Distributed Locking

Question 45

What is the primary challenge in designing consensus algorithms for highly dynamic systems with frequent node joins and departures?

Accepted Answer

Maintaining a consistent view of the membership across all nodes

Answer

Preventing malicious actors from manipulating the system

Answer

Ensuring data integrity in the presence of failures

Question 46

In a consensus algorithm, a node that is responsible for collecting proposals and coordinating the decision-making process is known as:

Accepted Answer

Proposer

Answer

Coordinator

Answer

Learner

Answer

Acceptor

Question 47

Which of the following statements about consensus algorithms is TRUE?

Accepted Answer

They are essential for building reliable and resilient distributed systems.

Answer

They can completely eliminate the risk of data loss.

Answer

They are only applicable to systems with a small number of nodes.