System Design Interview & Question Answers

1.? Explain the Load Balancing concept in system design.

Load balancing is the process of distributing incoming network traffic across multiple servers. It ensures no single server bears too much demand, preventing any server from becoming overwhelmed and possibly failing.

2. Describe the CAP theorem and its implications in distributed systems.

The CAP theorem states that a distributed system can only guarantee two out of three properties: Consistency, Availability, and Partition tolerance. In real-world scenarios, systems typically prioritize either Consistency and Availability (CA systems) or Availability and Partition tolerance (AP systems).

3. What is caching, and how does it improve system performance?

Caching involves storing copies of frequently accessed data in a location that's faster to access than the primary storage. It improves system performance by reducing latency and decreasing the load on the primary data source.

4. Explain the difference between SQL and NoSQL databases.

SQL databases are relational databases, while NoSQL databases are non-relational and can handle unstructured data. SQL databases use a schema for defining the structure of data, whereas NoSQL databases are schema-less.

5. What is sharding in the context of databases?

Sharding is a database architecture pattern where data is horizontally partitioned into smaller, more manageable pieces called shards. Each shard is stored on a separate database server, distributing the load and improving scalability.

6. Describe the concept of microservices architecture.

Microservices architecture is an approach to developing a single application as a suite of small services, each running in its process and communicating with lightweight mechanisms like HTTP APIs. It promotes modularity, scalability, and ease of maintenance.

7. What is the role of a reverse proxy in system design?

A reverse proxy acts as an intermediary between client applications and backend servers. It can perform tasks such as load balancing, SSL termination, caching, compression, and security enforcement, improving the overall performance and security of the system.

8. Explain the concept of eventual consistency.

Eventual consistency is a consistency model used in distributed computing where, after a certain period of time with no new updates, all accesses to a system will return the same result. It allows for high availability and partition tolerance in distributed systems.

9. What is the role of a message queue in system architecture?

Message queues facilitate asynchronous communication between distributed components. They store messages sent from producers until they are consumed by consumers, enabling decoupling of services, fault tolerance, and load balancing.

10. How does data replication work in distributed databases, and what are its benefits?

Data replication involves copying data to multiple locations. It provides fault tolerance, high availability, and reduced latency. When one replica fails, the system can continue functioning using the data from other replicas.

11. What is the purpose of a CDN (Content Delivery Network) in web applications?

CDNs are geographically distributed networks of servers that work together to deliver digital content (web pages, images, videos) to users in a faster and more efficient manner. They reduce latency and improve website performance by serving content from servers closer to the user's location.

12. Explain the concept of consistent hashing and its applications in distributed systems.

Consistent hashing is a technique used to distribute data across a cluster of servers. It provides a way to evenly distribute data while minimizing the number of keys that need to be remapped when the size of the cluster changes, making it useful in distributed caching and distributed databases.

13. What are RESTful APIs, and how are they different from other types of APIs?

RESTful APIs are a set of constraints that are applied to web services. They use standard HTTP methods (GET, POST, PUT, DELETE) and are stateless, meaning each request from a client contains all the information the server needs to fulfill that request. RESTful APIs are designed for scalability and simplicity.

14. How does authentication and authorization work in a microservices architecture?

Microservices often use tokens (like JWT) for authentication. Once a user is authenticated, authorization checks are performed at each microservice based on the claims within the token. Access control lists or role-based access control mechanisms are commonly used for authorization.

15. What is the role of a leader election algorithm in distributed systems?

Leader election algorithms are used to ensure that all nodes in a distributed system agree on which node is the leader. The leader coordinates activities in the system, making decisions that are replicated across the nodes. It's crucial for maintaining consistency and coordination in distributed systems.

16. Explain the concept of idempotence in web services.

Idempotence means that an operation can be performed multiple times without changing the result beyond the initial application. In the context of web services, idempotent operations are crucial for ensuring that repeating a request multiple times has the same effect as making the request only once.

17. What are WebSockets, and how do they differ from traditional HTTP connections?

WebSockets provide full-duplex communication channels over a single TCP connection. They enable real-time communication between clients and servers, allowing both to initiate communication. Unlike traditional HTTP connections, WebSockets don't suffer from the overhead of repeatedly establishing new connections for each exchange.

18. How do you design a system to handle high availability and fault tolerance?

To achieve high availability and fault tolerance, redundancy, replication, load balancing, and failover mechanisms should be implemented. Redundant components, backup systems, and graceful degradation strategies are also essential. Regular testing and monitoring ensure that the system can quickly recover from failures.

19. What are the security best practices in designing a distributed system?

Security best practices include data encryption in transit and at rest, proper authentication and authorization mechanisms, regular security audits, patch management, and adhering to the principle of least privilege. Employing firewalls, intrusion detection systems, and secure coding practices are also vital.

20. Explain the role of Docker and containerization in system design.

Docker and containerization technologies provide a way to package applications and their dependencies into standardized units. Containers offer consistency across different environments, improve scalability, enable faster deployment, and enhance resource utilization by allowing multiple isolated applications to run on a single host.

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