System Design: How to design Twitter? Interview question at Facebook, Google, Microsoft
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- čas přidán 9. 07. 2024
- Designing the architecture of Twitter and similar social networks is a popular engineering interview question asked at companies like LinkedIn, Microsoft, Google, Snapchat, NVidia and others. This interview question is extremely broad but gives you the opportunity to talk about technologies like in-memory databases, replication, sharding etc. It's important to give a clear high level overview of the problem, ask clarifying questions and talking confidently about strengths and weaknesses of the proposed solution. Every architecture has trade-offs and interviewers want to hear you talk about them.
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Details taken from a presentation of the VP of Engineering at Twitter: www.infoq.com/presentations/T...
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Nice effort and really explain the things. Please mention the sources you have referred. This would allow us to go in-depth of a topic.
Can you please also add low level design?
In some orgs they asks HDL and LLD. How would you classify this? I think these boxes you drew were HLDs but the tables and ER diagrams would be part of LLD right?
I wanna get into Amazon, how can I get your referral?
Great job!
I know html, css, js, reactjs for frontend, python for backend, and mysql. Now I want to understand how to glue these together, build an application and deploy on server.
What do I need to learn next?
Is this the right video?
man i cant express my happiness. you are the only one on youtube(infact the internet) concentrating on high level systen design. many companies are shifting their focus from algorithms to system design now a days. it was so hard to figure out how to come up with answers to these. Your videos are a life saver sir. You people are literally changing lives. the minimum i can do is say a big thank you to you for making these vids.
+Biswajit Singh I‘m really stoked to hear that, man! Happy I can help you out. You would do me a huge favor if you could share my videos on your social networks. There will be more interesting videos to come! 👍
The minimum you can do is pay your first month salary to his patreon account, if he has one.
For that I’ll make a Patreon 😄
companies arent shifting focus, as u r becoming senior, u r facing more architect lvl questions.
Check "Tech Dummies".. .he is much better then him
I used the caching strategy described in this video in my system design interview. You are part of the reason why I received an offer from one of my dream company. Thank you!
hi, what caching strategy is described in this video? The Redis fan out part? Could you elaborate more? Thanks!
@@ethanlyu4839 Yes, the Redis fan out for active users, but I wasn't asked exactly to design Twitter. I borrowed this part of the design in my answer.
What design interview question u got ?
Can you share ? It would be of great help for me.
@@jeevithatd9221 just look up github repo for: system-design-primer . It covers a lot of the most common system design questions as well as giving you the fundamentals before giving you the problems.
I'm halfway there and just overwhelmed with the kind of explanation this guy has put into the videos. Probably will complete this and come back again for more such videos. Thank you!
Very few people explain as well as you do and cover these topics. As a software engineer, I am very interested in these topics, and the community needs more videos like this! Keep up the good work!
Hi Ramon. Thanks for making these SDI videos. There are quite a few important things missing from this video to be considered a complete and correct answer in a real interview: the list of different micro/services that makes the platform run. Full database design/schemas. API commands from client to server and in between important micro services. And most importantly - “back of the envelope” estimations I.e. number of users DAU, QPS, storage requirements, throughout requirements etc.
I hope you’ll continue making SDI videos that contain this info too in the future. Many thanks and best of luck
Thanks for doing this! One suggestion: You should have separate playlist for system design and algo related questions.
+Venkat Raman That’s a good point, will do! Thanks
Time flew, amazing stuff man. Crazy ideas are being implemented when it comes to huge systems.
This was amazing! Thank you so much, as a beginner on System design, you explained it beautifully.
Great video :) really happy to see someone explaining overall system design in depth. Waiting for more exiting videos on system design.
Thank you so much for posting this video. This is great! Many regards.
Thanks for this insight with great simplicity. Hope to see detailed videos on followup topics as well.
Thanks!
Awesome video. Thank you. It gives me a basic idea about how to approach system design questions. This design covers a lot of things which is used in real-world huge systems. It includes relational databases, In-memory databses, hashing, load balancers and most important how to design system based on actual requirements, like eventual read consistency in case of twitter.
Your videos have been amazing. They are a great complement to other videos that are more algorithm focused.
I'm committed to watching your design video once a day till i finish them... then repeat. Thank you.
Love it :D All the best!
It was a very good head start into how I can approach a problem. Thanks a lot.
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I actually shared this with my newsletter for acing coding interviews. Great way of identifying problem areas and solving them
Hello Mr. Lopez! I loved this video. But it is always very likely to face a system design question totally out of what you had prepared for an interview. So a video on all possible system design components and how they are used for specific use cases in real life products can be very useful. So once building blocks are available, its easier from there. For example, REDIS database with its in-memory function is a good takeaway from this video which I can use in different scenarios.
Thanks for your feedback! I‘m planning something alone those lines. Don‘t forget to subscribe ;)
I have an upcoming test about distributed databases and WDM, this has been such a help in considering how to answer these problems. Thank you!
8:06 great breakdown by system traits to design improvement. Network access availability > consistency
9:27 I like how you go into higher lvl overview with actual scenario/api for when tweets made
The best design interview videos in your channel.
Fantastic video. You can also optimise ram needed and computational load by having a redis cluster per region and by tracking where reads come from per user to only rebuild their timeline in regional clusters they are likely to read it from. (Dont worry about rebuilding my timeline in the UK if I only ever read from Australia). Of course you can divide the computation that way too with at least a worker per region. Also you can optimise the read requests themselves by only loading the most recent slice of the timeline and loading in the next slice when you scroll to the very bottom.
This is great! Your approach, time management and advise to solve the problems are spot on. Thank you and keep up the good work!
+Ravi M Hey Ravi, thank you for the kind words! Stay tuned for more videos :)
Wonderfully explained. Excellent stuff. Thank you much.
You save my life! Thanks!
excellent job!!! Thank you very much for sharing.
What I like about your explanation is that u r not rushing it by preparing the content beforehand. Many of the videos does that cramming so much information in very little time. You are carefully walking thru the solution giving us ample time to make sense of a point u made. Can you suggest some resources(books,articles,lectures,seminars, utube channels like urs) to read/watch to get good at system design
Thank you for this video. I guess it’s the best one on the topic
Extremely grateful for your videos!
Glad you like them! If you want to support the channel and future content please share my videos and spread the word on your social media =)
I have looked into couple of other twitter system design videos, but I felt your videos are way more explanatory. Your video answered my questions like "how the redis node is choosen out of many?", "for users with thousands of followers and uncertain about their next login, will constructing home timelines for such users is worth it?". I believe your design is not complete w.r.t analytics and search functionality, but still very informative and nicely explained. Thank you.
Thank you!
Where is unique tweet id created?? immediately after load balancer? How will it be consistent and unique with other distributed servers once created on fly?
Really fascinating, many thanks. Hardly in the Internet can you find such content 🎉
Thank you a lot for taking your time and aring this awesome video.
This guy is awesome! Subscribed
Fantastic tutorial. It certainly helped me to get a perspective of the system design. Keep rocking and thanks for helping the world !
Thanks for the kind words!
I learned interesting things from this video but it was also pretty historical. I mean, I'm not sure how much signal I got about his design skills and tech leadership capabilities; I can tell he knows how Twitter works.
Thank you so much!! :)
today I was asked this question during an interview which makes me wonder what is the gain in asking something that pretty much can be memorized from videos just like typical common algorithms questions, I really don't see too much gain in companies expecting you to play to 'design the internet' I came up with something similar to this but replacing redis with temp tables 🌬️🔥 thanks for the info
Awesome explanation and Thanks
Great video. Thank you
Amazing video on System design. Your way of explaining things is simple and on high level. Many thanks.
Thank you!
I liked the video before i finish the first 5 mins! thanks a lot for the great video =)
Thanks! Glad to hear :)
awesome video. Thank you for sharing!
Great video. Thanks. You make system design interesting. Tnks
Thats very helpful, thank you
Miles to go before you sleep.
Could you please prepare system design and LLD for the following:
1. Simulation of a cricket match, football match etc.
2. Implementation of Queue like Kafka
3. Ecommerce price drop notification system for 50M products
4. Amazon like website and order management system i.e. everything that happens after clicking checkout
5. Elevator system
6. Scrabble
7. Chess game
8. A library for evaluation of expression
Thank you a lot sir for the amazing content please upload more
Here are few others design / architecture which i am curious to know ... would be great if you could create them in the near future:
1. CZcams architecture and design or similar video streaming websites
2. Amazon or any E-commerce website
3. Instagram
4. Google Search Engine
Thank you so much for this!
+Fahran Kamili You are very welcome!
Your content is amazing. You should create Udemy course on System Design Interview Questions.
Excellent Vdo for beginners like me.... Thanks a lot man.... :)
really great video!!!!!!!Keep it up!!!!!!!!!
your every word is useful and informative!!!
This is genius thank you!
It's a wonderful explanation about Tweeter Timeline, User Followers in details with respect to the system design. That really rare and deep in terms of getting advanced topics that most of the top-level organization ask to clarify and see their confidence. Thank you so much for the sharing perfect video which I was eagerly searching for. I would like to request you one more topic about - Google Map and Gmail system design in detail. Thanks in advance. Better Luck.
Thanks a million!
Awesome video and stuff.. I was trying hard to get hold of Design Solutions but could not find good content.... Keep it up and continue making great videos... :)
+ankita gupta Thanks, Ankita! I‘ll do my best :D
thank you for these videos. they are very nice and well explained.
+Copacel You‘re very welcome!
Thanks a lot for the video. it helps us to think the system design in a broader perspective.
I have two questions here. You said conventional Relational Database would be a bottleneck in this kind of systems. Does NOSQL would be the ideal one here for storage?. Also during the entire video, you have talked about In Memory Database. At what point of time, this data gets persisted into the database?
He mentioned there should be a machine between the Load balancer and the redis clusters. I would guess that machine would take care of persisting the tweet into the database (preferably in an async manner)
Yes, it will get persisted in NoSQL for sure, As @cats3xxx mentioned. Initial POST and GET will always happen on Redis and I see his design shows Redis is kind of persistence cache for faster tweets flow.
Hello, is RabbitMQ is a good choice for user notifications feature in webapps like twitter/fb ?
thank you very much for valuable post
Love ur tutorials. Please do a system design for a ecommerce website
amazing tutorial just subscribed
really good video. Thanks a lot
Thank you.
Love that!
+Maciej Jordanek Happy to hear that :D
It will be great if the architecture of maintaining hastags in twitter can also be explained: Search, top trending hashtags etc.
This is a great video. I have a quick question with using list in Redis. The video only mentioned store the tweet_id and sender_id for Bob's list. What about the actual tweet? Is the actual tweet store in Redis and we will need to do a look up by each tweet_id to get the actual text?
I believe tweet gets also stored in redis, considering its only text+links. It wouldn't be much useful if we still have to fetch tweets from DB.
Saving all the tweets for entire duration could be memory and computation intensive.
Hence, I believe twitter uses time expiration mechanism in Redis. redis.io/commands/ttl
I can say this because it takes only few seconds in you're looking at your feed. On the other hand, it takes more seconds for a query when you search it on Twitter.
Why do we store 3 times in redis?
Sriram Subramanian To handle failures of cache nodes utilizing a number of replicas
I loved it 😍
at 9:46 he says the tweet will hit a gateway, then proceeds to draw a load balancer. anyone care to explain what comes first and how they're related to each other? (is load balancer and gateway the same?)
good video helpfull i will show to my team .thank you
Thankyou for sharing this descriptive video. This is definitely the cleaner strike as you were aware of some of solutions and tech stack that Twitter has already incorporated. I would however more interested to know how the tweets with the visual content would be handled. May be some exploration toward CDN and CMS related solutions? I can understand covering all aspects in one video is not possible for anyone and would look forward for more contents posted by you. Great Going!!
can we simulate a basic scalable setup like this in cloud, like AWS, and test the performance ?
The only thing I didn't like about this video is that I can only like it once. What a great Video!!!
What's the rationale for having 3 Redis databases instead of 1? Optimize recovery time based on user location/server load? Thank you!
Great video, thanks a lot. Shouldn't load balancer connects to servers and the servers access external persistent memory like Radis?
Radis is in-memory which is very fast compared with external database. Moreover, fetching data from external DB is much costly
Redis boxes are servers by themselves. You can decide to put your in-memory caching either in the same machines that are serving the initial HTTPs requests or have a dedicated fleet (most used).
Nice one!
Hi, Can you please do a video on designing a service like google docs and how to keep everything in sync, concurrent writes by multiple users etc
Great video. Thanks for taking effort to make it available for us all. A quick question if you can help me understand, wondering when is the tweet stored and where? Who can be responsible for such cases? Thanks!
I love your system design videos! They are so helpful for me to prepare for interviews. Would you be able to make a video for system design of gmail?
I love the video, thank you for doing this. To design the system like Tweeter in the time constraint of an interview, I would probably start with no caching layer whatsoever. Just bunch of distribiuted databases. In every case, REDDIS is typically in-memory and has to have a traditional database as its source. Another point I would cover is once the user is logged and receives his initial snapshot of timelines, how does Tweeter merge live updates into user timelines.. Then an interesting question is if half of your friends are local and half are on the other continent. How does twitter merge tweets with different latency profiles. In any case, thanks for doing it!!!
I'm confused: Why does the request reach the Redis cache right after reaching the LB instead of the request first reaching the LB, then an application server (a service), then a Redis cache? How does the cache know which records to search for? Does that mean that the API requires that each request contain hash information for the Redis cache and that the Redis cache is set up to manage HTTP requests?
From what I know Redis is more than an in-memory database, it does provide persistence. Am I wrong?
Thank you for the video, Sir! May I ask why you choose to mix the implementation details with the design, is it the standard practice? For instance, you mentioned Redis as a in memory DB in the diagram. Why not just leave it at "in memory DB"(the design) and leave out the Redis (the details). Much thanks!
Thank you
This is great! Can you talk about how to design a recommendation system like people purchased this product also bought these other products?
Thank you :D Yeah I‘ll take a note of this
after clarifying the requirements, wouldn't the next step to be understand the load patterns to the service? Wasn't jumping to the schema design a bad idea?
Why is it being replicated 3 times on the redis machine though? Why isn't one redis machine enough
To avoid a single point of failure. If there would have been only one Redis machine and it failed before persisting data into the database then data will be lost.
Thanks for the nice video, it is informative. I have two questions. 1) You mentioned that data will be duplicated on three reddis servers. How to are these three servers been selected? Do they intentionally choose three reddis in three different locations? For example, one in local (US), another at Asia, and another one at EU? Then, the question is what if the user travels to Australia? 2) I may missed it, is this design, sounds like one tweets will get duplicated at the home page of all followers. That means a lot of duplications, which will end up with much more memory/storage usage. Is there any way to relief this?
Hi, Can you please do a video on designing a service like Uber/Lyft? Including services like location based look-ups for cabs, computing route, fare etc. It seems to be a common interview question. Great job by the way.
+Eldo Joseph yes! Thats exactly what I have planned for the next system design video. Thank you!
Also designing a recommendation system please. Thank you so much for taking the time to make these videos. They are very helpful and resourceful. Glad and lucky to have come across your channel.
+Akshatha Thank you, thats always great to hear! I’ll do my best to make some more of these asap :D
Very clear
Thanks for a great video. I've got a couple of questions though. Q1. How do you maintain the followers' database? Is it denormalized for each user?
Q2. How often and when do you update the hashlookup (to find the correct redis instance)? What happens if that hashlookup server goes down? Should we add redundancy there?
Q1: Not necessarily. Looking up followers should be a fairly fast lookup based on an indexed key which is the userId.
Q2: Yes redundancy for loadbalancers are a must, you don‘t want a single point of failure there. By the way: There is going to be a new video this weekend about loadbalancing ;)
why does it redirect me to "Alice Johnson" profile when I click on link to follow on twitter
System Design is a discovery process, which means you start with a prototype stage to a production ready stage. It seems you demonstrated the final design, instead of starting with a standard design and improving on it incrementally based on the real-world challenges.
Exactly. It seems unreasonable an interviewee is going to come up with something like this that took Twitter years in 45 minutes. Would have been better to start form the ground up and build a reasonable system.
Can you please do a system design video on 2 topics
A) how do u make sure the number of simultaneous video streams somebody watching let’s say Netflix is only 3 devices at a time.
B) windows system update, how do u stream a windows system update to client computers ?
Thanks for the great video! I have a question regarding timeline - does the system stores the whole user's timeline from the beginning (in Redis), or some portion of the timeline? For example, from last login?
Depends on what your goals/constraints are, right?
According to the source video, they store about the last 800 tweets from a user's home timeline.
can u please make a video for designing online payment system
amazing Video!Thanks.Can you also add how to design LinkedIn?
Thank you so much :)...plz make design of Ecommerce like flipkart or amazon!!!