How to Answer System Design Interview Question.
Let’s delve into the art of acing system design questions. If you’re aiming for a technical role such as a software engineer or technical program manager, you’re likely to encounter a critical interview: the system design interview. Before we dive into the specifics of how to master this type of interview, let’s clarify its purpose.
Understanding the System Design Interview
This interview evaluates your knack for crafting system architectures to solve intricate real-world challenges. It’s important to grasp that the goal isn’t to create a flawless solution. Instead, it gauges your capability to blueprint an architecture, analyze complex problems, explore various solutions, and rationally assess their pros and cons. So, with the interview’s intent in mind, let’s explore how to approach it effectively.
Navigating the System Design Interview
Contrary to coding interviews, system design interviews typically feature open-ended design problems. This is where having a structured approach becomes invaluable. It aids in rapidly organizing your thoughts and methodically addressing the question — a pun that holds true since you’re essentially tackling a problem that would normally require a team of engineers and condensing it into just 45 minutes.
A framework serves as your guide, helping you manage your time efficiently, communicate with utmost clarity, and logically build toward a fruitful resolution. Once you’re familiar with this framework, you can consistently apply it to navigate any system design interview question.
Introducing the Framework: Five Essential Steps
Step #1: Defining the Problem Space
In this initial step, our focus is on understanding the problem at hand and establishing the scope of the design. This involves a comprehensive examination of the issue and a gradual refinement of its scope. To achieve this, it’s pivotal to pose numerous questions. The goal is to transition from a broad and vague challenge to a more precise and narrower one.
It’s imperative to refrain from leaping into the design process without completing this crucial step. Clearing up any ambiguity in the problem is essential. You should explicitly outline both the functional and non-functional requirements. These two facets, functional and non-functional requirements, dictate what’s included and what’s excluded from the scope of your design.
During this phase, it’s advantageous to articulate your assumptions and decisions to your interviewer. This offers them insight into your thought process and guides them through your approach. Think of it as leading your interviewer on a guided tour. Make sure each step is communicated explicitly as you progress. Moreover, consider whether you’re constructing the system from scratch, who the intended clients or users are, and whether interactions with existing system components are required.
Additionally, pay heed to the non-functional aspects of your system design. These elements might be tied to business goals or user experience. Examples include factors like availability, consistency, speed, security, reliability, and even cost. In case you’re confronted with a plethora of design constraints, prioritize the most crucial ones. Ensure you communicate your reasoning behind this prioritization to your interviewer. It’s prudent to stay receptive to your interviewer’s cues; if they guide you in a particular direction, be attentive.
While it’s essential to be thorough, remember that you’re not obliged to perfect every requirement at this stage. Striking a balance between comprehensiveness and progress is key. Ultimately, you need to advance to the next phases of the interview process.
Estimating Data:
The subsequent step entails estimating the volume of data you’ll be handling. This estimation informs decisions such as storage size and bandwidth requirements. It also provides a preliminary insight into potential scaling needs in the future. You might also formulate assumptions about user volume and behavior patterns. However, always validate these assumptions against your interviewer’s expectations.
Remember, the foundation of a successful system design interview lies in your meticulous approach to defining the problem and understanding its dimensions.
Step #2: High-Level Design
In this phase, we’re delving into the high-level design of the system. This step involves outlining the core components of the system and demonstrating their collaborative functionality, all while adhering to the constraints established in the previous step. The focus here is on presenting a foundational overview; you don’t need to delve into intricate details at this stage.
To begin, we lay out the design of APIs. These APIs serve as contracts governing how clients can access the system’s resources. Each system requirement should be translated into one or more APIs. It’s important to choose the appropriate type of APIs for your system, such as REST, SOAP, GraphQL, or RPC. Equally crucial is explaining the reasoning behind this selection. This step also involves considering request parameters and response types. These APIs serve as the bedrock of your system’s architecture.
Following the API design, contemplate how communication between the client and web server will occur. This paves the way for creating a high-level design diagram that illustrates the interaction and interplay of various components.
Creating a Comprehensive Diagram:
A diagram serves as a visual blueprint of your design, highlighting the most essential components required to meet functional requirements. This diagram becomes an instrumental tool to showcase to the interviewer how data and control flow within your system. However, at this juncture, it’s not yet necessary to delve into the scalability aspect of the system; that exploration comes in the subsequent phases.
Keep in mind that this high-level design phase sets the stage for a clearer understanding of your system’s architecture. It offers a holistic view of how different components collaborate to fulfill the system’s objectives.
Step #3: Deep Dive
In this stage, we dive into the depths of the design, enabling a more thorough exploration of system components and their interconnections. While the interviewer might offer guidance, it’s important not to solely rely on them to steer the conversation. Your proactive approach is key to initiating and shaping the dialogue.
Begin by delving into how non-functional requirements wield influence over your design choices. For instance, if an online system demands up-to-the-minute data, contemplate strategies for expediting data ingestion, processing, and querying. Similarly, when dealing with vast volumes of data, contemplate database partitioning to balance storage and query load. Factors such as load balancer layers might also come into play to distribute read and write traffic.
This phase demands meticulous consideration, and while there isn’t a single definitive solution, it’s pivotal to present a range of design alternatives, complete with their respective merits and demerits. Furthermore, elucidate why a specific option takes precedence over others, given the contextual conditions. This exercise underscores one of the primary skills evaluated during the interview — your ability to analyze various design choices critically and determine the most suitable approach for the given circumstances.
Step #4: Scaling and Bottlenecks
In this pivotal step, we shift our focus to identifying bottlenecks and opportunities for scaling. After delving deeply into the system’s intricate components, it’s time to zoom out and evaluate the system’s capacity to function seamlessly under varying conditions and accommodate future growth. Here are some key considerations to keep in mind:
Addressing Single Points of Failure: Evaluate whether the system is susceptible to a single point of failure. If such vulnerabilities exist, brainstorm strategies to enhance the system’s robustness and elevate its availability.
Replication and Data Value: Assess the value of the data being handled. Determine whether data replication is necessary. If replication is pursued, weigh the significance of maintaining consistency across various versions.
Global Service and Data Locality: If the system supports a global service, deliberate on the deployment of multi-geographical data centers to optimize data locality. This enhances user experience by minimizing data transfer latency.
Managing Usage Patterns: Examine whether any exceptional usage patterns, such as peak time usage or specific user behavior, could negatively impact system performance. Plan for accommodating these patterns without compromising performance.
Scaling Considerations: Devise strategies for scaling the system to accommodate a significantly larger user base. As the system scales, it’s crucial to explore approaches for upgrading individual components gradually or even migrating to a different architecture.
Leveraging Key Concepts: Here’s where your familiarity with concepts like horizontal sharding, content delivery networks (CDNs), caching, rate limiting, and the distinctions between SQL and NoSQL databases proves invaluable. These concepts provide tools for optimizing performance and handling increased user demand.
In essence, this step involves a holistic evaluation of the system’s capacity to handle diverse scenarios and its potential for expansion. By anticipating and addressing potential bottlenecks while harnessing the power of scalable solutions, you’re ensuring the system’s robustness and resilience in the face of growth and evolving usage patterns.
Step #5: Review and Wrap Up
In this concluding phase, we undertake a comprehensive review and wrap up our system design endeavor. This step encompasses summarizing the key decisions made throughout the design process, offering a concise yet thorough rationale for each choice, and acknowledging any trade-offs in terms of factors like space, time complexity, and more.
A Comprehensive Overview: Present a clear and concise summary of your major design decisions, ensuring each is accompanied by a well-founded justification. Highlight any compromises or trade-offs you’ve encountered along the way.
Meeting Requirements: Double-check that your design effectively addresses all the requirements outlined at the onset of the interview. While it’s advisable to intermittently ensure alignment with requirements throughout the process, this step provides a final opportunity to confirm everything is in order.
Exploring Improvement Avenues: While your design solution is comprehensive, it’s also prudent to point out areas where further enhancement or refinement could be pursued. This underscores your capacity to envision continuous improvement.
As we conclude this interview, it’s essential to reiterate the design’s highlights, its alignment with requirements, and its readiness to tackle the problem at hand. Remember that this interview typically spans around 45 minutes, with around five minutes allocated for introductions at the outset and the chance to ask any questions of the interviewer toward the end.
With this step, we neatly bring together the elements of our system design journey, ensuring a coherent presentation of decisions, justifications, trade-offs, and future considerations.