Mastering Microsoft system design interview as software engineer

Are you a software engineer preparing for the system design interview at Microsoft? You came to the right place!

A bit of personal background: I worked on cloud storage as a software engineer at Microsoft for 6 years, before moving on to Meta.

During my time at Microsoft, I interviewed dozens of SWE candidates. Given my role on the Azure team working on distributed systems, my focus in interview loops was often system design interviews.

System design is an essential skill for senior technical positions, such as senior software engineers or engineering managers at Microsoft. The company still values exceptional talent with such skills. You can ace the system design interview at Microsoft with proper guidance, top-notch content, practicing design problems, and, of course, dedication.

In this blog, I’ll walk you through Microsoft’s interview process, discuss the importance of the system design interview, and explore the top system design questions by Microsoft and their solutions to help you land a job as a Microsoft engineer.

If I had to pass the Microsoft system design interview again, this is exactly how I would do it.

Microsoft system design interview#

The interview process is almost similar in top tech giants with slight variations. At Microsoft, it typically entails the following steps:

Now that you’re more familiar with the interview process, let’s explore how to ace the system design interview round at Microsoft.

Understanding the system design interview#

System design focuses on building and engineering scalable systems. A good system design requires you to think fully about a system’s infrastructure. A system design interview (SDI) is a technical evaluation of a candidate to build robust and scalable systems. Unlike coding interviews with a single solution, SDIs are open for discussion with multiple possible solutions that can further be re-iterated.

In SDIs, the questions are vague and open-ended to analyze the interviewee’s ability to approach a problem and their technical knowledge. Therefore, getting ready for a system design interview isn’t just about grasping technical details; it’s also about understanding the problem, breaking it down into parts, and coming up with the most optimal solution.

Why does Microsoft value system design?#

Microsoft has products with millions of active users, and the number is also increasing. Therefore, the company needs capable and talented individuals with system design skills to build and maintain scalable systems. The first and most important thing to value system designs is the practical implementation of knowledge.

Other reasons to value system design interviews are that they ensure a candidate can effectively solve complex problems, design scalable solutions, be innovative and creative, communicate the reasons effectively, etc. These skills are very important for a company like Microsoft because their products might face challenges, and for that, they would need someone who has the right skill set.

Microsoft’s approach to system design interviews#

Microsoft strategically approaches the system design interview with the following two parts:

1. Basic questioning about concepts: The first part focuses on analyzing a candidate’s knowledge of important concepts related to distributed systems and understanding of basic components. The questions can be about databases, CDNs, load balancers, APIs, etc.

2. A real-time approach to system design: The second part of the interview is a hands-on exercise to assess a candidate’s ability to devise an optimal solution to a design problem. The questions for this part of the interview are very open-ended, like designing a distributed file system such as OneDrive.

What are interviewers looking for?#

In both parts, the interviewers analyze your technical knowledge and ability to apply that technical knowledge to develop an optimal solution for a scalable system. They also focus on your problem-solving, creativity, and cultural attributes to decide whether to offer you a role.

In short, they are looking for individuals who can tackle technical challenges, are adaptable, are team players, and align well with Microsoft’s culture and values.

Let’s go through the important strategies to tackle the system design interview.

Strategies to ace the Microsoft system design interview#

Let’s start by answering a basic question: how would you design a system in an interview if you have no experience in building a real system? You’ll have to prepare yourself accordingly, and the following are the steps to help you crack system designs:

1. System design fundamentals#

We can start by exploring a few basic concepts of system design that you should be able to talk about during the interview. The system design guide covers all the basic topics as shown below:

2. System design components#

Now that you’re familiar with basic concepts, let’s go through the basic components of system design. These components act as building blocks—similar to Lego pieces—to architect a system. The important building blocks are given in the following illustration:

3. How to architect a system#

You can’t start solving a problem directly without a strategy. The best strategy is to solve the problem step by step. Whether you define vague steps or take a practical approach depends on you. It is advised to approach the problem with a systematic approach.

Approaching design with RESHADED#

To crack any complex system design problems, we use RESHADED, a high-level system design interview strategy. Using this approach to design a system can help you impress your interviewer. Each letter is an acronym for an important aspect of the system to consider, as illustrated below:

4. Key system design problems by Microsoft#

Below, we’ve listed some common system design problems that are asked in Microsoft’s system design interview:

Let’s discuss solutions to a few of the key system designs listed above. The best way to approach the problem is to use RESHADED or at least try to follow a step-wise approach, starting with clarifying questions about requirements.

Design a food delivery system—Uber Eats#

A system like Uber Eats should have the following requirements:

System design#

We can leverage a microservice architecture where distinct services handle specific operations. To meet our requirements, we’ll implement several services, such as a restaurant serviceManages search queries of users for restaurant listings, menus, and availability., order management serviceHandles order processing and is linked to payment and notification services., delivery management serviceManages and tracks order deliveries, integrating Google Maps for optimal navigation routes from restaurants to customers., etc., for the system to work seamlessly.

Workflow#

A restaurant service handles customers’ requests to list nearby restaurants, menus, and availability. Once a customer places an order, the order management service processes the request, triggers the payment service if required, and, if successful, triggers a notification service to notify both the customer and restaurant about the new order. Once the food is prepared, the delivery management service assigns a rider, finds an optimal route for the rider, and provides real-time updates to customers through a notification service.

Key considerations in design#

Questions such as how to achieve low latency, how to connect the nearest riders (delivery drivers) to the customers, what happens if any party is disconnected from the internet, etc., arise that need to be answered effectively.

We need to consider such critical aspects and scale the system to the right size for three entities: users, restaurants, and delivery riders. We also need to ensure real-time updates of the restaurants, orders, and delivery statuses, and we need optimized databases for such updates. To lower the latency, we can place restaurant data, such as videos, images, and menus, on CDNs.

We also need an efficient data retrieval mechanism with geospatial data to locate nearby restaurants. We also need to integrate a payment gateway for online payments. For both these, we opt for third-party services like Google Maps and Stripe, respectively.

We’ve prepared a guide on designing the Uber backend that addresses a few of the described issues.

Design a multiplayer game#

Designing a system like a multiplayer game is complex, including managing game resources, real-time communication (chat and audio), and gameplay streaming. The requirements for such a system are listed below:

System design#

Using microservices architecture is a suitable option for a multiplayer game. A task-specific service, such as a game, session, play, payment, real-time communication, and notification service, would greatly help with different functionalities.

Workflow#

We use a central service, such as a game service, where players connect, creating pairs based on skill levels and preferences. The session service manages sessions and synchronizes the players. A messaging service like Kafka or pub-sub facilitates real-time communication between players, allowing for in-game chat, voice communication, and notifications. The play service will handle all the game-related tasks like updating stats, checking player’s availability, etc. The payment service facilitates in-app purchases of assets.

Key considerations in design#

The multiplayer game system is resource-intensive and can crash with millions of simultaneous users. We can make it available by separating gameplay from other CRUD operations, limiting requests, and utilizing monitoring. Latency is important for real-time communication and for updating game stats. We can achieve it by replicating regional player data, lag compression, buffering data, and using a virtual private cloud (VPC).

The players are connected to the game servers, which are further connected to VPC to separate real-time operations such as gameplay.

We have a detailed chapter that discusses both system and API design aspects of multiplayer games to better understand the system and its design.

Design a reservation system—OpenTable#

OpenTable is an online restaurant reservation service with millions of users (they call them diners). Such a system has the following requirements:

System design#

The system looks simple, but it isn’t. It has two parts: one for managing diners and the other for managing restaurants. We can leverage different services to manage each of the two, i.e., diners’ service and the restaurant’s service. Moreover, for bookings, we use a reservation service; for payment, we use a payment service, and a notification service to notify about updates to both. This leads us to use a microservice architecture.

Workflow#

We use a load balancer to distribute the requests equally among available services. Diners search nearby restaurants and opt to reserve a table. The booking service holds the booking details (temporarily reserves the table), triggers the payment service for payments, and sends the confirmation to both diners and restaurant managers after success. In case of any updates, both parties are notified via the notification service.

Key considerations in design#

Reservations can drastically increase during a holiday or any event at a specific location. How does the system manage such an increase in load? How does the system remain consistent while processing bookings for the same restaurants? Above all, how does the system scale to such a level while being available?

To answer all these, we can take some steps, such as introducing surge pricing to incentivize more restaurants to be available during peak times, establishing a queuing mechanism to handle requests systematically, and using caching strategically to store frequently accessed data, like available restaurants, to quickly match diners’ requests. Moreover, throughout this process, the system prioritizes consistency with ACID transactions so that no two diners reserve the same table simultaneously.

Trusted system design interview tips#

Effectively answering system design interview questions depends on how you present your thought process to your interviewer.

As an interviewer at both Meta and Microsoft, I have seen highly experienced candidates leave a poor impression and fresh candidates leave a good impression during the interviews.

Some useful system design interview tips are listed below:

Make sure to avoid these common system design interview mistakes:

Next steps#

With this blog, I wanted to provide a few of my best tips for mastering system design interviews at Microsoft. As a next step, you can get hands-on practice with example design problems with AI mock interviews.

You can also explore more resources to learn the fundamentals of system design and get real-world practice with the example design problems from the following course:

Happy learning!