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System design interview questions can help you prepare better for your interview and crack it with ease. System design is an important part of software development because it is the key to building complex and large scalable systems.
It has been observed that many times junior and mid-level engineers and even experienced professionals find it difficult to clear the system design interviews. Therefore, you must prepare well for the interview. To prepare for the interview you can take help from the several resources and interview questions.
In this article, we present the 11 toughest system design interview questions that will help you land a job in top-tier and FAANG companies.
Our guide will help you prepare well for the interview and make a lasting impression on the interviewer with your knowledge and understanding of even the most technical aspects.
Also read: System Design Interview Guide
1. Explain What is the CAP Theorem
The Consistency-Availability-Partition Tolerance (CAP) theorem states that a distributed system cannot simultaneously guarantee C, A, and P. It can give only 2 out of the 3 guarantees, as seen from the above image.
- Consistency: The data should remain consistent even after an operation has been performed in the database. For instance, after the database has been updated, all the queries should have the same result.
- Availability: There should be no downtime in the database and it should always be available and responsive.
- Partition Tolerance: Even if the communication becomes unstable, the database system should always be functioning.
Also read: System Design Interview Preparation: Content Delivery Networks (CDNs)
2. What are the Differences Between Horizontal and Vertical Scaling?
Horizontal scaling is the addition of more computing machines to the network sharing the processing and memory resources across the distributed network of devices. Here, more servers are added while the traffic load is distributed across these devices efficiently.
On the other hand, vertical scaling is upgrading the resource capacity of a single machine or switching to a new machine with more capacity. It involves increasing the capability of the server without the need for manipulating the code.
You can learn the following table to answer this system design interview question:
| Category | Horizontal Scaling | Vertical Scaling |
|---|---|---|
| Load Balancing | It helps distribute the request traffic across multiple machines | The load balancer is not required |
| Failure Resilience | It is more resistant to application failures because of the availability of multiple servers | It is more at risk of failure because there is only one machine |
| Data Consistency | Data inconsistency is possible here because of multiple machines handling different requests resulting in the data being out of sync | The data will be consistent because only one machine is involved |
| Machine Communication | Network communication is very important due to multiple machines being involved | The communication process within the machine is very fast |
3. What is Load Balancing and Why is it Important in System Design?
The concept of efficiently distributing the incoming traffic across a group of different backend servers is known as load balancing. This collection of servers is known as a server pool. The modern websites are designed to serve millions of client requests and return the responses quickly and reliably.
In system design load balancing is required to efficiently distribute the traffic across each server so that they are properly utilized. Further, it helps ensure that no single server is overloaded with traffic while others do not get any traffic.
Following are some of the key benefits of load balancing:
- They prevent requests from going to unhealthy or unavailable servers
- Presents resource overloading
- It helps eliminate a single point of failure
4. Can you Explain the Latency, Throughput, And Availability of a System?
Answer this system design interview question by first telling that in system design performance is a key aspect because it helps make services fast and reliable. There are three key metrics to measure performance:
- Latency: It is the time taken to deliver a single message. It is usually calculated in milliseconds.
- Throughput: The amount of data successfully transmitted through a system in a given time is known as latency. It is calculated in ‘bits per second’.
- Availability: It is the amount of time a system is available to respond to the requests. It is calculated by dividing the system uptime by (system uptime + downtime).
5. How Do You Design a Web Crawler?
To answer this system design interview question, you can start by defining what is a web crawler. It is a service that collects information or crawls the entire internet and all the websites on it to fetch millions of web documents.
You can refer to the following image to answer this system design interview question.
6. Differentiate Between an API Gateway and a Load Balancer
It is a commonly asked system design interview question but a very tough one. An API Gateway is a single point for managing and securing the APIs. It can handle tasks such as authentication, rate limiting, protocol translation, etc.
On the other hand, a load balancer distributes the incoming traffic to multiple servers and focuses on optimizing the performance, availability, and scalability.
The key difference between them is that while API Gateway emphasizes API management, security, and protocol transformation, a load balancer handles traffic distribution and server load optimization.
7. How Would You Design a Platform Like Youtube?
This is a very interesting system design interview question and generally involves the candidate thinking outside the box and coming up with unique solutions. Through this question, the interviewer not only assesses your technical prowess but also evaluates your creative skills.
You have to consider that there are a lot of challenges concerning data storage, data indexing, and providing a streaming service. Further, scalability is another challenge you need to address while designing a platform like YouTube. It has to be fast and be able to support millions of users.
Also read: How to Crack Full Stack System Design Interview Questions ??With Example
8. What are the Most Important Aspects in Designing Autocomplete Functionalities?
In answering this system design interview question, you can say that the following are the most important aspects that need to be considered in designing autocomplete functionalities:
- A typehead suggestion
- Queries per second handled by the system
- Support personalization with suggestions
- The amount of data to be stored
9. How are Performance and Scalability Related to One Another?
If the increased performance is proportional to the resources added, then the system is said to be scalable. Typically, performance enhancement in terms of scalability is concerned with serving more work units. But, it also means that it should be able to handle more work units if and when the dataset grows.
The system will be slower for a single user only if there is a performance-related problem. On the other hand, the system might be fast for some users and slow for some others, indicating a scalability-related problem.
10. What is Meant By Caching And Explain The Various Cache Updating Strategies
The process of storing file copies in temporary storage, known as cache, is known as caching. It helps in accessing the data more quickly, reducing latency. However, a cache can store only a finite amount of data. As a result, determining and developing effective caching strategies is important.
Do not forget to talk about the following caching strategies while answering this system design interview question:
- Cache-aside: In this strategy, the application writes and reads data from the storage. However, this interaction is not direct as the application only looks for an entry in the cache. It is also known as lazy loading as only the requested entry is cached and avoids unnecessary data caching.
- Write-through: Here, the cache is the main data store on which the system reads and writes data. The cache then updates the database accordingly.
11. What Are The Various Consistency Patterns in System Design?
Consistency, from the CAP theorem, states that every read request should have access to the most recently written data. A problem of synchronization arises when multiple data copies are available.
Following are some of the consistency patterns:
- Weak consistency: It works well in real-time with use cases like VoIP, video chat, etc. This is because, after a data write, the read request may or may not be able to get the new data.
- Eventual consistency: Once the data has been written, the latest data can be seen by the reads within milliseconds. The data gets replicated asynchronously. This type of consistency pattern can mostly be seen in DNS and email systems.
- Strong consistency: After a data write, subsequent reads will see the latest data. Such data is replicated synchronously and is usually seen in RDBMS and file systems.
Also read: Amazon System Design Interview Questions
System Design Interview Questions: How Interview Kickstart can Help you?
Cracking a system design interview is a challenge even for the most experienced professionals. They must have a proficient understanding of the technical concepts and soft skills like excellent communication, the ability to work towards the team’s common goals, etc.
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Watch this video to learn more about the different aspects of system design that can be asked during the interview and how you can answer them to not only leave a good impression but also to clear the interviews.
FAQs: System Design Interview Questions
1. What is the Significance of System Design Interviews in Software Engineering?
System design interviews assess a candidate's ability to design scalable, reliable, and efficient systems. They test understanding of architecture, component interactions, scalability, and trade-offs, which are crucial for building large-scale applications.
2. How can I Prepare for a System Design Interview if I am New to the Field?
Start with understanding fundamental concepts such as databases, networking, and distributed systems. Read books like "Designing Data-Intensive Applications" by Martin Kleppmann, practice with mock interviews, and use online resources and courses to get hands-on experience.
3. What Resources Can Help Me Practice System Design Problems?
Books like "Designing Data-Intensive Applications," online courses such as Coursera or Udacity, platforms like LeetCode, and mock interview services are excellent resources. Additionally, study real-world systems and try designing smaller versions of them.
4. How Important is it to Discuss Trade-Offs During a System Design Interview?
Discussing trade-offs is crucial. It shows the interviewer that you understand the implications of different design choices and can make informed decisions based on the system requirements, constraints, and priorities.
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