How to Design a Rate Limiter in System Design Interviews (2026 Guide)

image_credit — ByeByteGo

Hello guys, if you are preparing for System Design Interview then you may have come across Rate Limiter, one of the essential Software architecture components along with API Gateway, Load Balancers, Distributed Caches etc.

It is also one of the most popular System Design interview topic and many of my friends and readers have told me that Rate limiting algorithms and concepts are often asked on interviews. 

I have personally seen this question three time last year when I was interviewing for FAANG and other top tech companies, so, yes its one of those questions which you must master in depth. 

In today’s high traffic, distributed system architecture where applications and services interact with many users and systems, maintaining stability and preventing abuse are paramount concerns.

And Rate Limiting helps with that.

Imagine we have a service which is receiving a huge number of requests, but it can only serve a limited number of requests per second.

To handle this problem we would need some kind of throttling or rate limiting mechanism that would allow only a certain number of requests so our service can respond to all of them.

A rate limiter, at a high-level, limits the number of events an entity (user, device, IP, etc.) can perform in a particular time window.

In the past, I have shared best System Design courses, books, websites, newsletters, cheat sheets, mock interviews, blogs, tips, System Design GitHub repos, and 100+ System Design Interview Questions and Problems and today I am going to share about Rate Limiter.

In other words, a Rate limiter is a mechanism used in software systems and network communications to control the rate at which requests or operations are performed.

It’s designed to prevent overuse of resources, protect systems from being overwhelmed, and ensure fair usage among multiple users or clients. It can be applied at various levels like application, API gateway, or network layer.

Rate limiters are crucial for maintaining system stability, ensuring service quality, and managing resources effectively in distributed systems and high-traffic applications.

By the way, if you are preparing for System design interviews and want to learn System Design in a limited time then you can also checkout sites like ByteByteGo, Design Guru, Exponent, Codemia.io, Educative , Bugfree.ai and Udemy which have many great System design courses

Similar, while answering System design questions you can also follow a System design template like this from DesignGuru to articulate your answer better in a limited time.

Following this template is actually one of the best thing you can do to start your preparation for any system design interview.

What is a Rate Limiter?

A rate limiter is a mechanism used in computing to control the rate at which certain operations or requests are allowed. It is commonly employed in various applications and systems to prevent abuse, protect resources, and maintain stability.

The basic idea behind a rate limiter is to restrict the number of requests or operations that a user or system can perform within a specified period.

This is done to prevent overloading a service, avoid unnecessary resource consumption, and protect against potential malicious activities or unintentional misuse.

Here’s a simple explanation of how a rate limiter works:

1. Define Limits: Specify the maximum number of requests or operations allowed within a certain time window. For example, you might allow only 100 requests per minute.
2. Track Usage: The rate limiter keeps track of the number of requests made by a user or system over time.
3. Check Limits: Before processing a new request, the rate limiter checks whether the user or system has exceeded the defined limits within the current time window.
4. Decision Making: If the user or system is within the allowed limits, the request is processed. Otherwise, the request might be delayed, rejected, or some other action taken, depending on the specific implementation.

And here is a nice diagram from Exponent that shows the Rate Limiter in Action:

Rate Limiter Algorithms

There are different algorithms and strategies for implementing rate limiting, depending on the requirements and characteristics of the system. Some common Rate limiting algorithms include:

• Token Bucket: Requests are granted as long as there are tokens available in a bucket. Tokens are added to the bucket at a fixed rate, and each request consumes one or more tokens.
• Leaky Bucket: Similar to the token bucket, but instead of tokens, requests leak out of the bucket at a fixed rate. If the bucket overflows, excess requests may be delayed or discarded.
• Sliding Window: Counts the number of requests made within a sliding time window. If the count exceeds the allowed limit, further requests are delayed or rejected.

Rate limiting is widely used in web APIs, network protocols, web servers, and various distributed systems to ensure fair usage, prevent abuse, and maintain system stability.

If you want to learn more then the Rate Limiter chapter on ByteByteGo by Alex Xu is a great resource, I learned most of my knowledge from there itself.

Here is a nice diagram from ByteByteGo which explains Rate Limiter working in simple words:

Best System Design Interviews Resources

And, here is the curated list of best system design books, online courses, and practice websites which you can check to better prepare for System design interviews. Most of these courses also answer questions I have shared here.

1. ByteByteGo: One of the best platform for System Design interview preparation by Alex Xu, author of popular System Design book. It contains all the content of System Design Interview book volume 1 and 2 and will be updated with volume 3 which is coming soon.
2. Exponent: A specialized site for interview prep especially for FAANG companies like Amazon and Google, They also have a great system design course and many other material which can help you crack FAANG interviews.
3. Codemia.io — This is a new website which I found a couple of month ago and it proved to be one of the best resource to level up your System design skills. It’s like Leetcode for System design where you can practice popular System design problems, draw diagrams and get feedback from AI powered system to improve your design. It got more than 120+ System design problem and OOP Design problem for practice.
4. “Designing Data-Intensive Applications” by Martin Kleppmann: A comprehensive guide that covers the principles and practices for designing scalable and reliable systems.
5. LeetCode System Design Tag: LeetCode is a popular platform for technical interview preparation. The System Design tag on LeetCode includes a variety of questions to practice.
6. “System Design Primer” on GitHub: A curated list of resources, including articles, books, and videos, to help you prepare for system design interviews.
7. Educative’s System Design Course: An interactive learning platform with hands-on exercises and real-world scenarios to strengthen your system design skills.
8. High Scalability Blog: A blog that features articles and case studies on the architecture of high-traffic websites and scalable systems.
9. YouTube Channels: Check out channels like “Gaurav Sen” and “Tech Dummies” for insightful videos on system design concepts and interview preparation.
10. DesignGuru’s Grokking System Design Course: An interactive learning platform with hands-on exercises and real-world scenarios to strengthen your system design skills.
11. “System Design Interview” by Alex Xu: This book provides an in-depth exploration of system design concepts, strategies, and interview preparation tips.

And, here is a nice system design interview cheat sheet to quickly revise essential System design concepts:

image_credit — tryExponent

Conclusion

That’s all about What is Rate Limiter and How it works. Rate Limiter is an important tool in any Software architects hand and you can put it where you want to prevent resource exhaustion.

It’s also one of the essential concepts to learn for a System design interview. Many companies also ask about designing an API Rate Limiter. I mean you may be asked to design an API Rate Limiter which will throttle users based upon the number of the requests they are sending.

Remember, the interviewer is not just looking for the perfect design, but assessing your approach to problem-solving, your technical knowledge, and your ability to make reasoned decisions under constraints.

Other System Design Articles and Resources you may like

• Top 5 Places to learn System design and Software design
• Is DesignGuru’s System Design Course worth it
• 16 best Resources to Prepare for System Design Interview
• 100+ System Design Interview Questions and Problems
• Is Exponent’s System Design Course worth it?
• 16 Best System Design Interview Resources for Developers
• Is System Design Interview RoadMap by DesignGurus.io worth it?
• 10 Reasons to Learn System Design
• Review — Is Codemia.io a Good Place to Learn System Design for Interviews?
• 6 Best System Design and API Design Interactive Courses
• Top 5 System Design YouTube Channels for Engineers
• 10 Best Places to Learn System Design
• How to Prepare for System Design Interview
• Is ByteByteGo really worth the hype?
• 10 Software Design Courses for Developers
• 5 Best System Design Newsletters for Interviews
• My Favorite Software Design Courses
• 3 Places to Practice System Design Mock interviews
• Is Designing Data intensive application book worth reading?

Thanks for reading this article so far. If you like this system design tutorial then please share with your friends and colleagues. If you have any questions feel free to ask in comments.

P. S. — By the way, DesignGurus.io also have many other Grokking courses to prepare for essential coding interview topics like OOP Design, System Design, Dynamic Programming etc and you can get access to all of their courses for a big discount by joining their All course bundle. You can also use code GURU to get 30% discount.

All Courses

Buy all courses together to save 35% and have lifetime access.

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System Design Interview

System Design Concepts

Software Engineering

Stop Failing System Design Interviews: The Ultimate 2026 Prep Guide with Questions & Resources

image_credit — DesignGuru.io

Hello guys, if you are preparing for coding interviews but wondering how to prepare crucial System design topic and looking for step by step guidance with right approach, tips, and questions then you have come to the right place.

Earlier, I have shared best System design courses, books, cheat sheets, websites, mock interviews, and 25 System design interview questions and in this article, I will share a complete guide to crack System design interviews.

The Software Engineering job market is on fire! Especially if you have a couple of years of experience under your belt.

And in the world of Software Engineering, if you are applying for a Senior Engineer / Lead / Architect / or a more senior role, System Design is the most sought-after skill, and hence one of the most important rounds in the whole process.

If you mess this up, nothing else would matter. If you get it right though, you’re looking at a raise of at least tens of thousands of dollars annually.

So how do you ace your system design round? Well, here’s what I did while preparing for my interviews with Facebook, Google, and Amazon, and it worked out rather well.

I did end up creating a checklist for myself which got me through most of my rounds, so if you follow a similar path you should be able to come up with something that works for you as well.

Before we get into the details though, what is a system design interview? What do the interviewers really expect from the candidates?

image_credit — codekarle

What is Expected form Candidate during System Design interviews?

The first step to prepare for System design interview is to understand what is expected from you? Once you know that you can align your preparation strategy to meet those expectations.

So here are the key expectations from you on a System design interview:

1. You should be able to design a system that satisfies the requirements given to you and scales well, for example design Twitter, design a vending machine or design a trade position aggregator.
2. Your design should be pluggable and not restrict the addition of new features.
3. You should be able to compare various alternatives and choose the most optimal one. Things like, which database is the most important, or which protocol should you use, or what’s the best approach to scale a system, etc.
4. You should know the basics that are relevant from a system design standpoint like:
5. Load balancers
6. APIs
7. Caches
8. Databases
9. Network Protocols
10. Message queues
11. CDNs
12. High-level details about ML and Big data
13. CAP Theorem
14. Monitoring and analytics

These are actually the essential System design topics and concepts every developer should prepare. If you have knowledge about these topics then you will definitely do well on system design interviews.

By the way, don’t get overwhelmed by number of topics, most of the good System design course like System Design Interview Guide by CodeKarle on Udemy or Grokking the System Design Interview on DesignGurus.io covers all these topics. This course by Design Gurus has helped 60k+ subscribers to crack their system design interview (SDI).

Grokking the System Design Interview | The #1 Online Course

Grokking the System Design Interview is a comprehensive course for system design interview. It provides a step-by-step…

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How to prepare for System Design Interviews?

While many things have changed in last a couple of years, the System design interview has also changed with more focus towards API, performance, and Microservices.

Any way, here is a simple four-step process to ace any System Design round, not just this year but also in coming years.

1. Master Essential System Design Concepts like Scalability, Consistency, Caching, Database sharding and replication etc.
2. Learn from the tech giants by reading their blogs like Uber and Netflix
3. Practice System design questions like designing YouTube, WhatsApp etc on sites like Codemia.io which contains more than 120+ system design problems. It’s a Leetcode for system design.
4. Practice and Mock Interviews (like tryExponent, Codemia.io, Bugfree.ai or DesignGuru )

1. System Design Concepts

Any system design interview will definitely require you to come up with a basic high-level design for whatever system you are trying to build. There are some components that will be needed for sure. Make a note of these components.

Here are a few of them:

1. Load Balancer

You cannot have a distributed system without a load balancer to distribute the incoming requests among various nodes. This ensures proper resource utilization and that there is no single point of failure in your system. Here’s how Nginx does it.

While learning about Load balancer its also good idea to learn about API Gateway and carefully understand the difference between load balancer and API Gateway, which is quite important from interview point of view. This question has been already asked to me a couple of times on interviews.

2. Caching

If you have ever done performance improvement then you know that the Caching is probably the first thing which comes in mind. Most systems have some read-heavy interactions, some information that the user will access frequently but not update as much.

It makes sense to cache this information in such a way that it can be easily fetched without the need for a DB lookup.

Think low latency.

Also, based on your use-case, you might need to store more frequently accessed information or more recently accessed information. So, read up on various eviction policies like least recently used (LRU).

If you want to learn more then ByteByteGo System Design course have a lot of information on Caching strategies and how to effectively use caches. You can refer them to learn more.

3. Database

Database is one of the most important skill to have as most of the real world application you will build will have some sort of data store like relational database or NoSQL.

In fact, there can be no system without some form of data storage. Whether you want to store files, images, product information, financial transactions or simply dump all the data from various user interactions to run analytics later.

It all needs databases. So read up on it. Find out what matters when you are selecting a database, read about SQL/NoSQL, query patterns, and how CAP theorem might come into play while making tradeoffs.

Sandeep has explained this quite well on his System Design course on Udemy, if you want to learn further, you can refer that as well.

4. Message queues

Sometimes our system needs to perform some tasks that need to be done but not necessarily immediately, or their outcome does not affect the user’s journey.

In such cases, rather than making a service call, and waiting for the response, it makes sense to just write the message to the queue so that it can be executed later.

This is also known as asynchronous messaging which is backbone for many Microservices.

What if you need to insert information in your database, and bulk insert could be more efficient? It would make sense to just keep track of these inserts in a message queue and perform 1 bulk insert instead of hundreds of 1-to-1 inserts to optimize your resources.

A good knowledge of Messages queues like RabbitMQ, ActiveMQ, and Apache Kafka is essential for any Software Engineer and this is one topic which is covered quite well on Educative.io’s Grokking Modern System Design for Software Engineers & Managers course. If you want to learn about not just message queue but other essential System design topics, this is one resource which I personally use.

5. CDN

When your users are distributed geographically, getting your content to them in a reasonable amount of time becomes a real challenge.

CDNs allow us to maintain a copy of our data in various data centers located closer to the users’ location to reduce the latency.

Here is a short video about how Akamai does it.

6. Analytics and Monitoring

This is something that is needed in every system you create. This is a hidden requirement, no one calls it out in the requirement gathering but every interviewer wants this.

User logs in or logs out? Wish listed an item? Payment failed? It is all the information for us! Anything of importance happens, fire an event and save it in your messaging queue.

You can perform real-time analytics on data or just dump it in a Hadoop cluster to use later. Similarly, if an API call is regularly failing, or if your servers are about to run out of resources, wouldn’t you like to know of it beforehand?

A good knowledge of tools like Grafana, Prometheus can help with you with Analytics and monitoring and also to impress your interviewer during system design interview.

Alex Xu has also shared a lot of good information on Monitoring on his book and ByteByteGo course, you can refer them as well.

7. Network Protocols

Based on your requirement, based on the type of content you are sharing, you might need to make a decision on which network protocol to use. 

Read up on various network protocols like TCP and UDP and when are they relevant, what might be the compromises you might need to make, etc.

The first step is to know about all these concepts. And by knowing concepts, I don’t mean just some theoretical knowledge of what these are, but more practical hands-on experience about what should be used when.

You need to know things like:

1. Which is the best alternative to choose from, given the use-case.
2. What are the tradeoffs that you need to consider while making these decisions?
3. Best practices for certain use-cases.

To know most of these things, I’ll recommend going through this course on System Design by CodeKarle, which covers all of the above with concrete examples from the real world.

2. Learn from the tech giants like Uber and Netflix

This is probably not going to help in the short term. But in the long term, to become an expert in System Design, 

It’s best to look at the Tech blogs of various tech companies and see how they are solving various technical problems.

This would paint a clear picture of the real problems that they face and how innovatively they solve them.

Understanding these things would help you become better at system design and also keep you up to date with the latest innovations in tech.

Some of the best blogs to follow are:

1. Facebook engineering blog
2. Netflix tech blog
3. Uber engineering blog

If you don’t like reading and prefer watching then you can also join online courses created by ex FAANG employees like the Mastering the System Design Interview by Frank Kane , (Ex Amazon Hiring Manager). This is one of the best resources to learn System design for interviews.

3. Solve Frequently asked System Design questions

An obvious way to get started with your interview prep! Knowing the basics is definitely important, but it won’t be enough! The most basic way to get started with your practice is to look at some frequently asked questions and their solutions.

Most system design interviews revolve around some 5–6 commonly asked System design questions and if you know the solutions to those, you are more than likely to clear this interview.

The most common questions are (with solution, click the link to see the solution when get stuck):

1. How to design Twitter?
2. How to design a Chat system like WhatsApp or Facebook Messenger
3. How to design Ticketmaster?
4. How to design an efficient Parking Lot?
5. Whatsapp System Design
6. Airbnb System Design
7. Uber System Design
8. Tinyurl System Design

If you need resources to solve these questions, something which not only solves the question but also explains the underlying concepts and approach to solving system design questions then this highly-rated course by CodeKarle discusses most of these case studies and some more problems, which has helped many people crack their interviews for companies like Google, Facebook, Microsoft, Amazon, etc.

4. Practice (Mock Interview)

Practice, practice, practice! Did I say practice? There are a lot of resources out there. I have shared a few that discuss some of the most popular system design problems in detail.

Once you go through a few of them you will start noticing a pattern and will soon be able to come up with solutions on your own.

You should also get a better understanding of how your systems are designed in your organization. How are the other teams doing things? What factors do they take into consideration?

The next best thing is to practice with a friend. Make sure you also go through a few mock interviews before your actual interview to avoid some common but easily avoidable pitfalls.

Since chances for companies like Google and Meta is hard to come by you should prepare as best as possible and Mock interviews are really important for them. They allow you to see your actual preparation level before real interviews.

At the same time, its also important that your mock interview should mimic the real interview and for that I recommend you to join sites like tryExponent, Codemia.io, Bugfree.ai, Designgurus.io or , which allows you to take mock interview with real experts.

Master System Design & Behavioral Interviews Like Leetcode

Prepare for software engineering interviews with 150+ system design and 30+ behavioral questions at bugfree.ai. Get…

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Codemia.io is like the Airbnb for mock interviews and career coaching. It connects job seekers with seasoned FAANG interviewers who provide invaluable feedback, getting you ready for real-life interviews.

Many of my friends, readers, and colleagues along with numerous job seekers have already reaped the benefits of this platform.

What makes Codemia stand out?
1. Affordability: The average cost per session is significantly lower compared to other platforms.
2. Expert interviewers: Veterans from FAANG and top-tier companies bring years of experience, offering priceless feedback that truly makes a difference.
3. Direct communication: Job seekers can directly message interviewers to address any questions or concerns, such as experience sharing or rescheduling, ensuring better preparation for both parties.
4. All-in-one tools: Meetapro equips you with the essential tools for an effective interview session, including recording options for post-session review.

That’s why I highly recommend to add Codemia.io in your preparation journey for best results. You can learn more about it

Codemia | Master System Design Interviews Through Active Practice

No upcoming interviews scheduled. Schedule an Interview Create or Browse Add your available times or browse slots…

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Common Mistakes to avoid on System Design Interviews

Some most common mistakes that I have seen people make are:

1. Not driving the interview
2. Not asking questions
3. Not structuring the interview properly
4. Running out of time
5. Not considering the requirements
6. Not exploring all the alternate design options

All these mistakes can be easily avoided by having a few mock interviews with someone who knows System Design well. And time your interviews. The target must be to reach a solution within 40 minutes, including time for some discussion.

Well, that’s it, folks. With this 4 step process, you’ll soon be ready to ace any of your system design interviews! Hopefully, this should be a good starting point for you. Happy learning!

For mock interviews, you can also checkout Exponent website, which offer offer 1–1 coaching and classes for in-person learning and also run a free service called Pramp that offers peer-to-peer interviews for software engineers in data structures and system design.

System Design Interview Course - Exponent

This track provides in-depth walkthroughs and videos of the most common system design questions that are asked in…

www.tryexponent.com

If you need another option then DesignGuru also have mock interviews which cost around $239 and you get a chance to interviewed by experts and former Facebook Engineer and founder of DesignGuru.io 

Arslan Ahmad

Best System Design Interview Resources

If you need more resources like books, and online courses to prepare for the System design Interview here are my recommendations:

• CodeKarle’s System Design Interview Course on Udemy
• Grokking the System Design Interview on DesignGurus.io
• Mastering the System Design Interview by Frank Kane
• Codemia.io for Practicing System Design Problems
• Software Design and Architecture Specialization [Coursera]
• System Design Interview course and Mock Interview by Exponent
• System Design Interview Course on ByteByteGo by Alex Wu
• Web Application & Software Architecture 101 [Educative.io]
• Pragmatic System Design [Udemy Course]
• Grokking Modern System Design for Software Engineers & Managers

Grokking Modern System Design for Software Engineers & Managers - Learn Interactively

Distributed systems are the standard to deploy applications and services. Mobile and cloud computing combined with…

www.educative.io

Thanks for reading this article so far. If you like this System design interview preparation guide, questions, tips, and resources then please share it with your friends and colleagues who are preparing for tech interviews. If you have any questions or feedback then please drop a note.

All the best with your interviews.

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