Are you planning to interview for the SDE position at top MNCs??!! If yes, this blog will help you tackle System Design interview questions immensely.
Big software corporations have begun to ask system design questions as a part of their hiring process. Therefore it becomes critical to have in-depth knowledge of system design interview questions. The most vital and likely system design interview questions will be covered in this blog. Happy reading, Ninja!
What is System Design?
System design is an umbrella term for defining all the aspects related to architecture, Database configuration, modules, interfaces and product design of a system. System design aims to have a solid fundamentals-based approach to building a robust, resilient and fast system. To design a “system”, formal in-depth requirements analysis is carried out.
Most Asked System Design Interview Questions 2024
Here are the 15 most common system design interview questions explained with their answers.
What are the critical metrics for measuring system performance?
What is the CAP Theorem?
What is Load Balancing?
What is Sharding?
What are the different types of scaling?
What is Caching?
What is CDN?
What is a proxy server?
How is the NoSQL database different from SQL?
What is consistent hashing?
What is a leader election?
What is endpoint protection?
What are microservices?
How will you design a tinyURL system?
How would you design a search engine?
Let’s dig into these in detail.
1. What are the critical metrics for measuring system performance?
The most critical metrics are
Latency: It measures the system's response time in milliseconds.
Availability: It is the ratio of uptime to total time. Availability shows how much time the system was available to handle requests.
Throughput: It measures data flow per unit of time, usually represented in bits per second.
2. What is the CAP Theorem?
CAP (Consistency-Availability-Partition Tolerance) theorem states that all three parameters cannot be fulfilled simultaneously. More specifically, only two of three can be guaranteed simultaneously.
Consistency: The database should be consistent across all endpoints, i.e. after a post request, all queries should give the same response.
Availability: The system should be available all the time.
Partition Tolerance: The system should be tolerant of unstable networks.
3. What is Load Balancing?
Load balancing refers to efficiently distributing incoming network traffic to several servers. Load balancing helps mitigate the risk of too much load on a single node. By spreading the traffic evenly, load balancing enhances application responsiveness. It also helps in improving availability.
4. What is Sharding?
Sharding divides an extensive logical data set into smaller chunks known as shards. Here partitioning is horizontal. These smaller partitions are faster and easy to manage. Each fragment is stored on a separate server instance to spread the load. Some critical data is stored on each shard, but most data are different.
Sharding helps scale by providing increased throughput, high storage capacity and availability.
5. What are the different types of scaling?
There are two types of scaling:
Horizontal scaling is adding more nodes to the existing network to boost its performance. The workload gets distributed to the newly added nodes, which reduces the average load per node.
Vertical scaling refers to upgrading raw hardware resources such as processors, RAM, SSD etc. There is no need for code modification to achieve vertical scaling.
Horizontal Scaling
Vertical Scaling
Load balancing is required.
Load balancing is not required.
More resilient to single-point failures.
Less resilient as a failure of only one node is needed to crash the entire systems.
Lower consistency.
Highly consistent.
No limit to server capacity.
Limited capacity due to maximum limitations of the latest devices (RAM,CPU, etc).
6. What is Caching?
A cache is a high-speed local data storage layer that stores parts of frequently used data. Caching refers to storing frequently used data to be served quickly without searching through a more extensive database. Since the capacity of the cache is limited, the cache update algorithm must be robust enough to adapt according to data needs.
7. What is CDN?
CDN(Content Delivery Network) is the network of servers spread globally to serve static files such as HTML, CSS, JS etc. The purpose of CDNs is to reduce the response time of requests by having data centres geographically close to the end-user. Streaming companies such as NetFlix also use CDN for better performance.
8. What is a proxy server?
The word ‘proxy’ has the dictionary definition as ‘substitute’. Proxy servers act as the middleman between client and server. All the requests coming from clients can be masked with the help of proxy servers. VPN is based on the concept of proxy servers. In complex system designs, proxies can be helpful. For example, you can use a reverse proxy to serve requests you don't want the central servers to handle.
9. How is the NoSQL database different from SQL?
NoSQL
SQL
Non-relational
Relational
2. Dynamic schema with no proper structure
2. Use predefined schema to store structured data
3. Horizontally scalable
3. Vertically scalable
4. Uses key-value pair
4. Tabular style
5. Better for unstructured data such as JSON
5. Better for row-based operations on data
10. What is consistent hashing?
Hashing is the process of converting a given input into preferably an integer. In system- design, hashing is a critical step of load balancing. When a hashing algorithm is deterministic, it produces the same output when the same input is applied multiple times. For example, if the string ‘hello’ produces 10001 as output, then whenever input is ‘hello’, the output should be 10001. A deterministic hashing algorithm is known as consistent hashing when applied in system design.
11. What is a leader election?
The process of selecting a server to act as the leader of a group of redundant servers is called leader election. Leader election can also be done to choose a server to work on a specific task, such as updating the APIs, so there is no collision. Redundancy helps achieve higher levels of availability and consistency, but one must maintain proper sync. While selecting a leader, in case of leader failure, appropriate consensual algorithms are put in place.
12. What is endpoint protection?
When designing a large-scale system, it becomes critical to avoid too many processes that are not important to run on the system. For example, a user can click on a button multiple times when in an irritated state. Imagine the system has to serve all the incoming requests. Thus endpoint protection is needed to save resources.
In some situations, we will want to limit the times a user can request a service. For example, paid API services. The word ‘protection’ is used intentionally because it protects the system from cyber-attacks leading to DoS( Denial of Services).
13. What are microservices?
Microservices are an architectural and organizational way to develop software, where software is made up of small components communicating through a well-defined set of APIs. It helps to build scalable software which is easy to manage and upgrade. Each small service is autonomous and specialised.
14. How will you design a tinyURL system?
A technical interviewer might ask you this question to test your understanding of systems engineering fundamentals. You should explain the concepts behind URL, its advantages and disadvantages and the underlying concepts. Shortening of URL has several advantages. Let them know how you will handle errors and build a real-time shortening service or bulk shortening algorithm. Let us look at the answer to this system design interview question.
15. How would you design a search engine?
You should not think of just Google or Bing when hearing search engines. A company can have its search engine access internal information quickly. The interviewer might ask you this question in an actual design interview to check your understanding of indexing, crawling etc. Be prepared to answer these questions in detail. Let us look at the answer to this system design interview question.
More System Design Interview Questions
16. Define the architecture of a web crawler.
A web crawler is a service similar to a search engine like Google. It indexes website content across the Internet, ensuring its availability in search results.
Required features:
The service developed should be highly scalable to collect information from the web and fetch millions of results.
Updated information should be fetched every time the user requests a new query.
Some common problems encountered:
How to decide which search result should be given the priority index?
How would you manage the updates when the typing speed of the user is very fast?
Tips:
Learn more about crawling and scraping.
Study the URL frontier architecture to design this system.
17. How would you design an ATM system?
People use ATMs or Automatic Transaction Machines to deposit and withdraw money from their bank accounts.
Some required features:
Every user should have a bank account and a respective card linked with the account to carry out the transactions.
Each user would be authenticated with the help of a 4-digit secret pin.
Every individual can carry out only one transaction at a time.
Frequently faced problems:
What would be the outcome in case of a transaction time-out?
What actions should be taken if the funds are deducted from the bank account but not provided to the user through the machine?
Tips:
Break down the problem into different entities, such as Card and Card Reader, and define relationships or dependencies among them.
18. How would you design a streaming platform like Netflix?
Required features:
Continuous streaming of videos without any interruption.
Recommendation of videos to users according to their likes and dislikes.
Ratings and reviews of the videos.
Problems:
What will happen if many people are trying to access the same video at the same time?
Can there be lags in uploading and downloading videos?
Tips:
Cloud technology can be utilized to store videos.
The platform has three components: Content Delivery Network, Backend Database, and client device.
19. How would you design a scalable messaging system for a chat application?
The important points to be considered before designing a scalable messaging system for a chat application are:
Users can directly send messages to other users or chat in groups online.
Messages have to be stored for future reference.
Messages are to be encrypted to transfer them securely.
How would you know if a person is online or offline?
What should be done if a message fails due to a network error?
Would encryption of messages delay the transmission of messages?
How would you be notified if you have received a message?
Web sockets can be used for smooth bidirectional communication.
Bell notification can be used for receiving and sending messages.
20. How would you create your own recommendation system?
For creating a recommendation system you should first decide which domain the recommendation requires- e-commerce, websites, songs, food, etc. Solutions to problems like how would you get updated recommendations? should be analysed and given a thought to. You can also look into how you would train a model with the help of collaborative filtering.
21. How would you architect a system for parking lots?
Required features for the parking lot system:
The parking lot should be able to accommodate vehicles of all types: cars, bikes, buses, etc.
Decide on the cost of the different parking spots.
Challenges encountered:
What happens if two vehicles are assigned to the same parking spot?
What would you do if large vehicles were assigned to smaller parking spots?
Tips and suggestion that can be followed:
Look into the algorithms that would be the best fit for assigning the perfect parking spot for vehicles.
Enlist the entities required for designing the system
22. Design a service that shortens your URL.
Required features:
The resultant URL should be of a size smaller than that of the original one.
Navigation should be possible with the new shortened URLs
Support multiple user requests simultaneously.
Problems that you may run into:
What happens if two users enter the same URL?
How would you manage the storage?
What if a URL generated leads to the wrong site?
Tips and pointers:
You can use hashing to interlink the original URL with the newly generated URL.
For managing storage space, you can use the NOSQL database.
Multithreading can be used to manage traffic.
23. How would you design a tic-tac-toe game?
Points to be discussed before designing a tic-tac-toe game are:
There should be two or one external player and the computer.
The game algorithm should evaluate the winner and loser.
What happens if there is a draw?
How would you decide on the winning strategies?
If there is a draw, the players can go for another game.
If the computer is one player, then you can use the random method to generate random moves.
24. What are the key factors considered when designing a traffic control system?
Traffic control systems are important for managing traffic on busy roads. The Red, Green, and Yellow lights help manage the vehicles on the roads.
The system should be able to change the traffic lights based on the traffic rules. You should also consider problems like How would you decide on the time intervals between the transition of traffic lights? What would happen if the transition algorithm between the different lights went wrong? While designing the traffic control system you can use the state design patterns and the respective scheduling algorithms for transitioning the lights from one color to another.
25. How would you design a news feed system for Facebook?
The news feed feature of Facebook allows users to be aware of what is happening around him.
Some of the important features that the service must have are:
News feed posts can be images or audio, or video.
New posts have to come just after the news feed.
Problems:
How do you remove latency from the system?
Can the system survive a sudden user load?
How would the posts' priority in the news feed be decided?
Tips:
Sharding can be used to divide and share data across different systems and handle user load.
26. Briefly explain the architecture of Quora.
Required features:
Users should be able to create posts.
Real-time posting of comments.
The posts should be sorted according to the tags.
Problems:
Can the user upload images and videos, also?
Where would you save the images and other media?
Should there be an Android application for the system?
Tips:
To support high traffic, you can implement multithreading and load balancer.
Sharding can be used to divide and share data across different systems.
27. Design a system similar to Uber or Ola.
Required features:
The user should be able to book rides in real time.
Rides nearest to the user are be assigned such that the user can reach the destination as fast as possible.
It should be able to show the time of arrival and a GPS map of the destination.
Problems:
How would the geographical locations of the drivers be saved if they are constantly moving?
How would you decide on the fate of the ride?
Tips:
The concept of microservices can be used for faster booking of rides.
28. Can you explain the architecture and design principles behind global file storage and sharing services like Google Drive?
The following features and pointers are to be considered while designing a file storage service like Google drive:
The user should be able to add, delete, share, and edit files.
Any update in the file should be reflected in all other devices.
Where would you save the files?
How would you manage file updates?
What will happen if two users are working on the same document simultaneously?
Cloud storage technology can be used to store files.
Chunking can be used to split files into sections. This would support re-uploads of a particular section only rather than the entire file.
29. Outline the design of a type-ahead search engine.
Required features:
The suggestions in the services are to be refreshed depending on the update of the query.
A specific number of suggestions have to be displayed.
Problems:
When will the suggestions be displayed?
How will the suggestions be updated without any system lag?
How to decide on what will be the most suitable suggestion?
Tips:
Implement Natural Language Processing in the system to predict the next characters.
Markov chain rule can also be used to prioritize the queries.
30. Mention the features, problems encountered, and tips for designing an API rate Limiter system.
Required features:
The request count per second or hour should be considered.
The system should be able to handle the traffic.
The limiter should be informed if the requests are blocked.
Problems:
How would you count the number of requests at a given time?
Tips:
Use the sliding time windows to avoid hourly resets.
A counter integer can be used to save space.
Frequently Asked Questions
Q. How do you solve system design problems?
To solve system design problems, first break down the system into its components. Consider how they interact with each other. Important factors to consider are reliability, scalability, performance, and security. Use your creativity to apply design patterns, algorithms, and technologies.
Q. How do you answer system design questions in an interview?
To answer system design questions in an interview, break down the problem into manageable parts, consider the important requirements and suggest a suitable architecture, discuss trade-offs, and justify your design decisions.
Q. Why is system design difficult?
System design can be difficult due to its complexity. It requires various components, considering trade-offs, ensuring scalability and performance, and addressing real-world limitations to create a robust and efficient solution.
Q. What should I look for in a system design interview?
Focus on scalability, data consistency, fault tolerance, and efficiency while answering questions about system architecture. Demonstrate your ability to select the best databases, caching techniques, network protocols, and architectural designs to handle a variety of real-world situations.
Conclusion
Mastering system design interview questions is crucial for success in technical interviews. These questions not only test your knowledge of system architecture but also evaluate your problem-solving and communication skills. Practice, deep understanding of key concepts, and the ability to articulate your thoughts coherently will set you apart.
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