Facebook System Design Interview: Design Twitter

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Watch our mock Facebook system design interview. Kevin Wei (Coinbase PM) asks Hozefa (Facebook, Wealthfront EM) a system design question on designing Twitter.
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Chapters -
00:00:00 - Introduction
00:00:43 - Answer
00:01:00 - Requirements
00:05:18 - API
00:08:02 - Design
00:22:12 - Tips

[@tryexponent]

Don't leave your system design interview to chance. Sign up for Exponent's system design interview course today: bit.ly/2Nl5Bn5

[@stanleymakori777]

But the create API is only factoring in text mesages. What about posts that have videos or images ?

[@rrrrr16able]

If the quality of your courses are as bad as the current mock interview then I would rather never try exponent ..

[@ashwin81088]

This is a good interview. You designed twitter in 20 mins. Haters will say it’s not good.

[@nj1204]

We should at least do some back-envelope analysis on the MAU, DAU, QPS,etc for the non-functional requirement. We should also make it more interactive, i.e. check the feedback of the interviewer before jumping into the details of the API's. Maybe ask the interview to see if he wants to see which one first: high-level design, API, or data model?

[@wfan2844]

QPS, Storage and Network Bandwith estimation are required.

[@harshitkhandelwal8515]

He skipped the data model as well

[@usrenaem]

Thanks for the content! API structure is kind of out of common way to design restful apis. Don’t use verbs when it is possible.

[@Crack_interview_with_sim]

Very Bad idea giving name like gettweet ,createtweet . Basic naming of Rest API end points . Considering tweet as a resource just have GET and POST on it

[@adeelirshad228]

Agree.

[@comickracks6333]

Yes that's the design smell

[@anthonyc8579]

The geographic load balancing to different API servers part made no sense to me. When a user makes a request to a load balancer, they make an API request specifically to the load balancer and receive from it directly, so the don't make contact with the API servers at all. If you put the API servers in different regions, that would only be with respect to the load balancer, not the user themselves, so it wouldn't help at all since the load balancer is still in the same region. You'd need to do the geographic routing first before the load balancing step to do this properly, aka a traffic manager.

[@kk20299]

He is kinda nervous or not prepared. He used a load balancer instead of a traffic manager....

[@cpy]

This was pretty rough. If that’s what Exponent’s class teaches you then I’ll pass

[@igorborovkov7011]

not everyone wants to work at Albertsons, Walmart is ok for some

[@cpy]

@@igorborovkov7011 you base the level of learning on what company you are applying to? Aim higher for yourself, forget the company

[@saurabhtyagi1870]

@@cpy Nice

[@randxalthor]

Probably been asked on previous videos, but what software/website is used as the design visualization/scratchpad for the interviewees?

[@reevuadhikary]

Whimsical !

[@randxalthor]

@@reevuadhikary thank you!

[@Hanso1o317]

What app is it in the background?

[@shawnreichard5497]

Would it be good design to have the timeline as a queue. The queue would have a size that could perhaps be increased for people with lots of traffic. That way we store items that would be in the queue in the faster access database space and perhaps the stuff that would be maybe 3 queue away would perhaps be stored in a separate less frequently accessed storage (E3 perhaps?)

[@befuture_ru]

I like it 👍 What IDE do you use for the design prototyping?

[@nipunaggarwal8730]

Whimsical

[@janezhang1550]

For the timeline database, would it make more sense to store a list of tweet ids per user and then query the user database at runtime to compile the tweet text?

[@DigitalAlligator]

if you only store id, you need to use the id to query the database again, you still need to visit the same database. While in the timeline generator, the timeline already been build and just get everything all-in-once.

[@gustavoalves4324]

In this case we are sacrificing storage and consistency to have low latency, which is one of the non functional requirements. It would be way slower to fetch the timeline and then populate with the tweets from the tweets database, not to say we would be coupling the timeline service with the database used for creating tweets.

[@jojay6472]

Someone made this guy an EM lol

[@tushardhingra]

@exponent which tool is being used while answering the question?

[@tryexponent]

Whimsical

[@rajeshg3570]

To me it sounded like..this is very very high level design ..but in my opinion he could have added some details around some of the below aspects or at least get clarification on requirements to trim out some of these.. 1. Capacity planning 2. Type of DB and reason behind choosing that 3. Security aspects 4. High level db design 5. Tech stack ..for example.. aws s3 or cloud front or redis or Kafka etc 6. Scaling .. 7. peek load handling 8. caching mechanism

[@anonymously7777]

Lost at influencer service/timeline generation piece. Please elaborate to me how these services work

[@manoelramon8283]

sql db for tweets will be slow... timeline and feeds are different things

[@alexfomin1207]

What tool for creating the diagrams are you using?

[@tryexponent]

Hi Alex! The whiteboard tool being used here is “Whimsical”. They have a free and paid version so do check them out if you are interested!

[@harshitkhandelwal8515]

When interviewer asked for 80:20 question, I knew he was expecting to listen cache in the answer but the interviewee failed to catch that.

[@mohammadmonirhossain6214]

agreed

[@subhashismohanty5420]

The API names are not as per the standard. But overall good discussion.

[@jimmycheong7970]

Can definitely tell that this interviewee watched the Success In Tech version for this video. Like Chinese whispers, where unfortunately a lot of things are discussed at a high level and not enough rationale is explored. I mean he even says Lady Gaga for his example for influencers, word for word as in the Success in Tech video. Just saying 🤷🏻‍♂️

[@AshishShah1512]

This interview feels like it is given by a New Grad Software Engineer.

[@pratiks3044]

Cant agree more with you.

[@theafrodreamer]

Candidate seemed nervous

[@tommysuriel]

He didn't do any capacity calculations such as bandwidth and storage, is that ok for these interviews?

[@wfan2844]

probably not. If you ever interviewed with facebook, their prep doc says those calculations are 100% required.

[@vineethsai1575]

no, its probably a red flag.

[@innoirvinge8431]

its like only 24m system design interviews are like at least 35m

[@darkmadhavsharma]

cool makes sense.....

[@bhumir9279]

Appreciate content, but little average api design

[@ravindrabhatt]

Looks like he didn't prepare well for the interview.

[@vivekkaushik9508]

For a facebook program manager that's a potato quality webcam.

[@nicholasmanning4307]

One of the most horrible and unrealistic design interviews out there on the internet. Asks almost no questions (fundamental to design interviews). Not collaborative (also fundamental to design interviews). Doesn't add a space in front of "(" when writing in English. Super distracting and unprofessional. Breaks basic RESTful conventions with routes like /create/tweet

[@rrrrr16able]

This is a bad example of how you should not approach a system design interview

[@pinkylover911]

what is the meaning of mvp?

[@yassinezarir6428]

Minimum Valuable Product.

[@tryexponent]

Minimum viable product - the most basic version of a product you can ship to start getting feedback from users.

[@souvikghosh5668]

I was expecting more out of this. This was a waste of my time.

[@calvio2835]

a failed interview for both interviewer and interviewee. such low quality

[@42Siren]

This is too basic design. Unless the candidate has less than 4 years of experience, this should get rejected

[@JoyceCheng-hn3rm]

Does anyone else think this interviewer is annoying?

[@harshitkhandelwal8515]

Why? LMAO

[@fartzy]

This design was so mediocre

[@eurobeesbees3843]

This is a bad video. I would reject this candidate. The API design is too abstract, the get API is not right. FB system design interviews are surely not this easy. This person is very lucky to be at FB.

[@implemented2]

And where are you?

[@slavanikulin8069]

diversity hiring quotas

[@abp4708]

@@slavanikulin8069 helps to have interviewers that look like you. Less bias.

[@harshitkhandelwal8515]

He is at WealthFront and was at paypal for 8 years before that. Designing Twitter was asked in a FB interview hence the title