Your 7-Day System Design Interview Prep Plan
This article provides a structured 7-day plan to get you ready for a system design interview on short notice. In just one week, you'll revisit core system design concepts, practice designing both simple and complex systems (from a URL shortener to a Twitter-scale app), and end with a mock interview and final review.
If you’ve got a system design interview nearby, you’re probably staring at 100 different blogs, 50 YouTube videos, and an endless list of concepts like "CAP theorem," "load balancers," and "eventual consistency."
Take a breath.
You don’t need to know everything.
What you need is a focused, day-by-day plan to hit the most important concepts, build confidence, and avoid panic-prepping the night before.
That’s what this 7-day crash course is all about.
Whether you’re targeting FAANG or any top tech company, this guide will walk you through exactly what to cover each day — from understanding distributed systems to practicing real-world design problems like Twitter and Uber.
Let’s make your next 7 days count.
Day 1: Refresh Your System Design Fundamentals
Day 1 is all about reviewing the basics that every system design interviewer expects you to know.
Build or refresh your foundation in system design concepts.
a. Revisit Core Concepts
Spend today reading up on the essential building blocks of system design – think scalability, reliability, and performance.
Make sure you understand why we use components like load balancers, caches, databases, and proxies in large systems.
Check out System Design Interview Fundamentals that covers 25 key concepts (from caching and sharding to the CAP theorem and CDNs) that every engineer should know.
Skim through it and take notes on any topics that are unfamiliar.
b. Distributed Systems 101
Understanding how distributed systems work will help with any design question.
Key principles to recall include monolithic vs. microservices architecture and SQL vs. NoSQL databases – these often come up when discussing design trade-offs.
c. Know the Terminology
Ensure you can explain fundamental terms in simple words.
What exactly is caching?
How does a load balancer work?
What does the CAP theorem mean in practice?
Interviewers love when you can confidently define and then use these concepts in your designs.
By the end of Day 1, you should feel more comfortable with the fundamentals of system design. This strong foundation will make the rest of the week easier, since you'll be able to apply these concepts to specific problems.
Day 2: Design a Simple System (Practice with a URL Shortener)
Get hands-on by designing a small-scale system from scratch.
And starting with an easy design question will warm you up for bigger challenges ahead.
a. Pick a Simple, Common Scenario
A classic beginner-friendly design problem is designing a URL shortener (similar to TinyURL or Bit.ly). This is a popular interview question and a great way to practice the structured approach to system design.
Begin by clearly outlining the problem: we need to take long URLs and generate shorter aliases, then redirect users from the short link to the original URL.
Jot down the core functional requirements (e.g. generate unique short URLs, redirect to original, handle expiration or custom aliases) and non-functional requirements (high availability, low latency lookups, etc.).
b. Architect the Solution
Draw a basic design of the URL shortening service.
Identify components like an application server (to handle requests), a database (to store the mapping of short codes to original URLs), and a method for generating unique short IDs.
Think about how you'll ensure the IDs are unique (perhaps using a base-62 encoding or a hash function) and how to handle a high volume of reads (lots of people clicking short links) versus writes (creating new short links).
This is also a good time to consider caching frequently accessed links to improve performance, and note where a cache (like Redis) might fit in.
c. Use Resources for Guidance
If you get stuck, don't worry. Our detailed blog How to Design a URL Shortener Service walks through this exact problem step by step – from clarifying requirements to scaling the design.
Review it to compare with your approach:
Did you consider how to make the service highly available and fault-tolerant?
What about choosing the right database and designing a schema for billions of URL entries?
By the end of your practice, you should understand the key challenges (like handling a 100:1 read-write ratio or ensuring short URLs aren't guessable) and how to address them.
Spending Day 2 on a concrete example like this helps you practice the system design process: clarifying requirements, proposing a high-level design, and discussing improvements.
You'll use the same process for bigger systems in the coming days.
Day 3: Study a Complex System (Case Study – Designing Twitter)
Time to move on to a large-scale system design.
Understanding how real-world big systems are designed will prepare you for advanced interview questions and help you recognize common design patterns.
a. Pick a Well-Known System to Analyze
A great example is Twitter (or a Twitter-like social network).
This is a classic interview prompt for more experienced candidates – “How would you design Twitter?”.
Today, spend time learning how a system like Twitter is architected to handle millions of users, continuous streams of tweets, and real-time updates.
Start by breaking down what Twitter does: users post tweets, follow others, see a timeline feed, like/retweet, get notifications, search hashtags, etc.
Think about the core challenges such a system faces: massive scalability, high throughput (lots of reads/writes), and low latency (timelines that update in real-time).
Learn how to design Twitter.
b. Identify Key Components and Challenges
As you explore Twitter's design, note how it's solved certain problems.
For example, timeline generation is a central challenge – how do you construct each user's feed efficiently?
(Hint: systems like Twitter often use a combination of fan-out on write vs. fan-out on read strategies to distribute tweets to followers' feeds).
Consider the data storage: user data might fit in a relational database, but tweets and timelines could be stored in a NoSQL store for quick retrieval.
Caching is crucial here (e.g., caching user timelines or popular tweets to reduce database load).
Also, think about how microservices could be used (one service for user profiles, one for tweet handling, one for the news feed, etc.) to break the system into manageable pieces.
c. Learn from Existing Designs
As you go through the designs, relate those solutions back to the fundamental concepts from Day 1.
For instance, notice where eventual consistency is acceptable (Twitter might prefer availability over strict consistency for showing tweets) or how a distributed queue could help handle writes (like posting tweets or sending notifications asynchronously).
By the end of Day 3, you should have a solid understanding of a complex system's architecture.
Even if you don't memorize every detail, you'll gain confidence in discussing large-scale design trade-offs (like SQL vs NoSQL, or consistency vs availability) and see how fundamental concepts are applied in practice.
This knowledge will be invaluable if your interview asks you to design a big system or if you need to draw parallels to known architectures.
Day 4: Explore Another System Design (Case Study – Uber or a Messaging App)
Day 4 is about applying your skills to another domain, which helps reinforce your approach and uncovers new challenges.
Broaden your exposure by tackling a different kind of system design.
a. Choose a New Scenario
If you studied a social media system on Day 3, switch gears to something else today. Two great options are:
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Design a ride-sharing service (Uber/Lyft) – This type of system design question introduces real-time geolocation updates, matching algorithms, and dynamic pricing logic. The scale is huge (millions of drivers and riders), and the system needs to be highly responsive and reliable.
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Design a real-time chat or messenger service – Messaging apps (like WhatsApp or Facebook Messenger) emphasize low latency, high availability, and data consistency (no one wants to lose messages). They also deal with features like delivery receipts, group chats, and maybe multimedia transmission.
b. Touch the Specifics
For a ride-sharing service, think about the core components: rider apps, driver apps, a dispatch system to match drivers with riders, real-time location tracking, and a database to store ride data.
Key challenges include handling real-time updates (GPS coordinates streaming in), scaling the matching service during peak demand, and ensuring reliability (calls or messages between drivers and riders should always go through).
For a messaging system, consider how to maintain persistent connections (long polling or WebSockets), how to store messages (maybe with replication for durability), and how to scale to millions of concurrent users chatting.
After Day 4, you will have practiced designing at least two complex systems in different domains.
This broad experience is great for interviews: no matter what system you're asked to design, you'll likely be able to draw analogies from something you've seen (social network, ride-sharing, chat app, etc.) and discuss the relevant challenges and solutions.
Day 5: Focus on Key System Design Concepts & Gaps
Day 5 is a flex day to shore up any weaknesses and study important system design concepts that might not have been fully covered yet.
By now, you’ve identified areas you want more confidence in – use this day to address those and review advanced topics.
a. Review High-Impact Concepts
Think about the recurring themes in system design interviews and ensure you have a solid grip on them.
Common concepts include:
- caching strategies
- database scaling
- load balancing concurrency
- reliability techniques
b. Deepen Your Understanding of Trade-offs
Great system design answers often discuss trade-offs and alternatives.
Revisit topics like consistency vs. availability (from the CAP theorem), synchronous vs. asynchronous processing, or monolithic vs. microservice architectures.
Ask yourself: in which scenarios would you choose a SQL database over NoSQL (and vice versa)? When is it better to prioritize consistency over availability?
Make sure you can articulate these decisions.
Learn how to approach a System Design Question to structure your thoughts and cover all bases during an interview.
c. Fill in any Knowledge Gaps
Use this day to address any specific area you haven’t touched yet.
Maybe you realized you haven't thought about security (like authentication, rate limiting) or analytics and monitoring aspects of system design.
Or perhaps you want to quickly glance at one more system design example to expand your imagination.
Scan the list of Common System Design Interview Questions to see if there's a scenario or question type you haven't tried and read up on its solution approach.
The goal isn’t to memorize everything, but to ensure nothing major will catch you completely off guard.
By the end of Day 5, you should feel well-rounded in your system design knowledge.
You've reinforced core concepts, learned advanced techniques, and patched the holes in your understanding.
This sets you up nicely for the final stretch, where you'll practice under realistic conditions.
Day 6: Practice with Sample Questions and Mock Scenarios
Day 6 is about active practice – simulate the interview environment as much as possible with additional system design questions and possibly a mock interview run-through.
Transition from learning to doing.
a. Tackle a Couple More Design Questions on Your Own
Pick 1-2 system design interview questions from a list of common questions and try to solve them without looking at any notes.
Treat it like a real interview: give yourself a time limit (~45-60 minutes per question), sketch out your design on paper or a whiteboard, and talk through your reasoning out loud.
For instance, you could try designing an e-commerce system (like Amazon's order system) or a video streaming platform (like YouTube/Netflix).
These cover different challenges (e-commerce requires handling order workflows and inventory, while streaming deals with content delivery and buffering) and are great practice.
b. Refine Your Approach
After attempting a question, take a step back and evaluate your performance.
Did you remember to clarify requirements at the start?
Did you cover all major components in your design (clients, servers, databases, etc.)?
Did you discuss how to scale the system or handle failures?
Use the structured approach from the Day 5 review (requirements → high-level design → deep dive → trade-offs) as a checklist.
If you missed something, note it down so you won't forget in a real interview.
c. Simulate a Mock Interview
If possible, get a friend or colleague to act as the interviewer.
Have them ask you a system design question (maybe one you haven't practiced yet, to keep it spontaneous).
Then talk through your solution as you would in the interview, from gathering requirements to drawing the design and answering questions.
The experience of explaining your design out loud is invaluable – it highlights if you have any trouble articulating certain concepts or if you tend to go silent at times.
If no partner is available, you can still simulate a mock interview by recording yourself. Pick a question, hit record, and speak for 30 minutes as though someone is listening. You'll become more aware of your communication style and can self-correct any unclear explanations.
Practicing this way on Day 6 will build your confidence.
By now, you’ve done multiple designs and reviewed loads of material – today is about ensuring you can communicate that knowledge smoothly when the pressure is on.
Day 7: Mock Interview, Review, and Relax
The final day is here!
Day 7 is for one last full mock interview, a quick review of key points, and then giving yourself permission to rest.
By optimizing a mix of practice and relaxation, you'll enter your real interview sharp and confident.
a. Do a Final Mock Interview (with an expert if possible)
Treat today as your interview day rehearsal.
If you can, schedule a mock interview with an industry expert or use a professional service.
(For example, DesignGurus.io offers coding and system design mock interview sessions where you can get real-time feedback from experts.)
During the mock, approach it exactly like the real thing: listen carefully to the question, ask clarifying questions, outline your plan, then discuss and draw your system step by step.
Focus on communicating clearly and structuring your answer.
The feedback you receive will be golden – take note of any suggestions on areas to improve or points you missed.
b. Quick Review of Notes and Cheat-sheets
After the mock, spend a little time reviewing your study notes from the past week.
Skim through the fundamental concepts list from Day 1 to make sure terms like sharding, CDN, or eventual consistency are fresh in your mind.
Glance at any diagrams you drew for systems like the URL shortener or Twitter – visualizing them one more time can help solidify your understanding.
If you created a checklist of design steps (e.g., "1. Requirements, 2. Assumptions, 3. Core components, 4. Data model, 5. Bottlenecks & improvements"), review that framework so it's top-of-mind.
c. Relax and Recharge
Finally, give yourself permission to step away from studying.
A fresh mind will serve you better than cramming until the last second.
Do something to relax – whether it's a good night's sleep, a walk, or a favorite hobby – to get your mind off the interview for a bit.
Confidence is key in system design interviews, and it's easier to be confident when you're well-rested and not burned out.
Remind yourself that you've covered a lot in one week, and trust in the preparation you've done.
By the end of Day 7, you've effectively completed a week-long crash course in system design interview prep.
You've touched on fundamentals, practiced multiple design problems, and honed your interview technique.
Now, it's time to walk into your actual interview with confidence in your ability to think through any open-ended design challenge.
Conclusion: From One-Week Crash Course to Long-Term Success
Preparing for a system design interview in just seven days is an intense journey – but as you've seen, a week with the right strategy can make a huge difference.
This 7-day plan was all about maximizing impact: focusing on high-yield topics, learning by example, and practicing your communication.
By following this guide, you're not just cramming – you're building a structured approach to system design that will serve you in interviews and on the job.
Next Steps: If you found this one-week plan helpful and want to continue leveling up, consider taking your preparation further with guided resources. Our Grokking the System Design Interview course offers a comprehensive, in-depth curriculum with many more real-world design examples and expert insights.
Good luck with your system design interview!
FAQs
Q1. Can I really prepare for a system design interview in 7 days?
Yes, you can prepare for a system design interview in 7 days. With a structured plan that focuses on fundamentals, real-world design examples, and mock interviews, one week is enough to build confidence and deliver solid answers in your interview.
Q2. What should I study each day for system design interviews?
Day 1 is for fundamentals, Day 2-4 covers practical design problems (e.g., URL shortener, Twitter, Uber), Day 5 focuses on filling knowledge gaps, Day 6 is for mock questions, and Day 7 is for review and a final mock interview.
Q3. Do I need to memorize system design patterns?
Not exactly. You should understand common patterns (e.g., caching, sharding, queues), but focus more on applying them in context, explaining trade-offs, and solving problems methodically.
Q4. What are the most common system design questions asked in interviews?
Popular ones include designing a URL shortener, Twitter, Uber, messaging apps, and Dropbox. Interviewers also love to test how you handle scalability, availability, and trade-offs.
Q5. Where can I find mock system design interviews?
DesignGurus.io offers personalized mock interview sessions with expert feedback tailored to your skill level and goals.
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