System Design Interview Intro - Product and Infra Design Interview
March 5, 2024
In the ever-evolving landscape of tech interviews, the ability to design systems has become a crucial skill for aspiring software engineers. While coding challenges and algorithmic puzzles still hold their place, the rise of cloud computing, microservices, and distributed systems has brought a new dimension to the interview process: system design. It's no longer enough to write efficient code; you must also demonstrate an understanding of how to architect scalable, reliable, and fault-tolerant systems.
At its core, system design interviews test your ability to transform product requirements into technical architectures. This could involve designing a system for a ride-sharing app, a video streaming platform, or even a social network. The interviewer wants to see how you break down complex problems, identify key components, and make trade-offs between different design choices. It's a test of your problem-solving skills, your understanding of distributed systems principles, and your ability to communicate your thought process effectively.
Among all kinds of system design interview, product-oriented system design and infrastructure system design interviews are more common for general software engineering roles.
While product-oriented system design interviews focus on the business logic and user-facing components of a system, infrastructure system design interviews delve into the underlying infrastructure that supports these applications. This could involve designing a scalable and highly available data storage solution, a load balancing strategy, or a caching layer. These interviews often require a deeper understanding of networking, databases, and cloud infrastructure services.
It's important to note that system design interviews can also cover object-oriented design (OOD) and frontend system design. OOD interviews test your ability to design class hierarchies, implement design patterns, and model real-world entities. Frontend system design interviews, on the other hand, focus on the client-side architecture, including challenges like state management, rendering optimization, and offline capabilities. However, these topics deserve their own dedicated articles, as they each have their own nuances and best practices.
Product-oriented System Design Interview
Product-oriented system design interviews are all about designing the systems behind real-world products and apps. They're sometimes called "product architecture" or just "system design" interviews.
In these interviews, you'll get asked to design the backend for a particular app or service. For example, they might ask you to design the backend for a dating app, or a food delivery app.
Often, they'll describe the interview question in terms of a "use case" - basically a real-world scenario the app needs to handle. Like "design a backend for a dating app that lets people swipe and match." They'll sometimes name-drop a famous company too, for example "design the backend for a dating app like Tinder."
This guide will help you prep for those kinds of product design interviews. Here are some example questions to give you an idea:
- Design a pizza delivery app like Domino's
- Design a video streaming service like Netflix
- Design a marketplace app like Amazon
The key is taking a familiar app or service, and walking through how you'd actually design the backend system to make it work reliably at a huge scale. Don't stress though - we'll cover strategies to approach these step-by-step.
How To Ace Product-oriented System Design Interview?
To ace a product-oriented system design interview, start by asking clarifying questions. Don't jump into designing right away. Ask about key requirements, constraints, assumptions you should make, and which specific features need to be focused on. This helps scope the problem.
Lay out the major components/services needed. Break it down step-by-step. For a dating app you might need components like a matching algorithm, messaging system, database to store profiles, etc. Illustrate this with simple diagrams.
Get the high-level design right first. Resist getting too low-level at the start. Figure out how the major pieces fit together before diving into details.
After having the high-level overview, move on to considering key issues like scalability, reliability, security, etc. How will the design handle a huge number of users? How will you make it reliable and secure? This is crucial.
Be ready to dive into chosen areas more deeply once you establish the high-level design. The goal is to demonstrate your ability to break down complex problems, use fundamental software architecture concepts, and make pragmatic tradeoffs.
Infrastructure System Design Interview
Infrastructure design interviews are another type of system design interview you might run into, though not as common as the product design ones.
In these interviews, they'll ask you to design systems for specific infrastructure use cases - so lower-level, more technical stuff under the hood rather than user-facing products.
For example, maybe they'll ask you to design a system for caching data in memory, or a tool for coordinating tasks and jobs across a cluster of servers. Since it's getting into the weeds of system internals, the interviewer will focus more on your mastery of low-level system concepts like consensus algorithms, data durability, and so on.
Here are some example infrastructure design questions to give you a taste:
- Design an in-memory caching system like Redis
- Design a Job scheduler for running background tasks
- Design a distributed locking system for resources across multiple machines
The key difference from product-oriented system design is really honing in on those crucial system-level concerns like consistency, availability, partitioning, and optimizing for performance at low levels of the stack.
How To Ace Infrastructure System Design Interview?
Acing infrastructure design interviews is all about showing you really grok the fundamental system concepts and can apply them in a clear, structured way.
Just like the product-oriented system design interview, ask upfront questions to make sure you understand the requirements, constraints, and what exactly you're being asked to design. Get those scope boundaries nailed down.
Then, break the system down step-by-step into the core components and services it will need. Walk through each piece and how they fit together. Simple diagrams can help illustrate your overall architecture plan.
But don't go full "design at scale" mode just yet. Start simple by outlining a basic, centralized solution that handles the core use cases. Get the foundation right, then you can build it out.
As you iterate, start layering in all the real-world considerations - scalability, reliability, performance tuning. Talk through the major concerns and design decisions for addressing them. Consistency? Availability? Lock it down.
The interviewer will likely dig into specific areas, so be ready to really nerd out with technical implementation details on your chosen strategies and components. Don't just use buzzwords - show your true mastery.
Throughout, make sure you're evaluating the key tradeoffs for the design choices you're making. Every decision has pros and cons, so walk through your rationale.
Most importantly, let the interviewer follow your thought process by constantly explaining your thinking out loud. This isn't a test to see if you can recite sample architectures - it's about showing how you can break down and design systems systematically.
Use the right lingo too - your interviewer will expect you to demonstrate fluency in distributed systems concepts like sharding, replication, consensus protocols and so on.
By structuring your approach, weighing tradeoffs thoughtfully, and communicating the nitty-gritty implementation details, you'll show you've got the infrastructure design skills to thrive!