System Design Mock Interview: Design Instagram

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Күн бұрын

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In this interview, Jacob (Dropbox Software Engineer) answers a system design interview question of designing Instagram, commonly asked in software engineering and technical program management (TPM) interviews.
The diagramming tool we use is called Whimsical: whimsical.com/
Chapters -
00:00:00 Introduction
00:00:09 Question
00:00:35 Answer
00:01:13 Requirements
00:03:41 Scale
00:06:19 Data types
00:14:50 Design
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Пікірлер: 464

@meqdaddev4341 2 жыл бұрын

Great job.. Thanks for the video. I think we can add the following: - Elaborating the DB sharding and partitioning in the system. - DB Replication, by adding redundant blocks for database based on master/slave relation, where the master is for write, and slaves for read. - Talking about the data searching, like considering to use Elasticsearch for example. - Adding a block for CDN to clarify where it should to be in the system diagram. - Adding a message/uploading queue - Making an estimation for bandwidth

@sourabh258 Жыл бұрын

I think DB Replication is understood for default. Rest all points are great 👏

@igorbragaia4895 7 ай бұрын

This video is great introductory resource, however it is a little bit superficial. Anyway was great watching and looking forward for the other videos on this channel!

@BoNyKiD 3 жыл бұрын

"And then we can talk about the API a little bit later" Never talks about API

@josephmorales652 5 ай бұрын

I know my ass would not get hired if I did that.

@NianLi 2 жыл бұрын

A good to add would be message queue. As we know, when we update for example a big image, user shouldn't be waiting there for a long time. Also, if we write the huge chunk of data directly to to the image storage, it will explode (storage usually won't have such a big RAM)! Hence, a good practice would be push it to the queue with a publisher, and have multiple listeners to update these images data (binary formats) into the storage.

@lagneslagnes 11 ай бұрын

pushing large objects to S3 won't explode it

@coolY2k 9 ай бұрын

@@lagneslagnes and even if it did, where you would store 5mb image? In queue? Azure Blob/S3 are by design much more scalable than any queue that can handle 5mb binaries within a message.

@NithinMWarrier 3 жыл бұрын

Thanks a lot, you clearly explained how to draw the architecture diagram component by component and finally building the whole system. Other popular system design videos missing this.

@JamesMortenson-fz7ch Жыл бұрын

This is a great example of what you should strive to have completed at the halfway point of the interview.

@babybear-hq9yd 3 жыл бұрын

Unreal video! I'm relatively new to Systems Design but this was easy to follow and aligned with a lot of other good information I've been finding on the web. Thank you!

@tryexponent 3 жыл бұрын

Glad you liked it! Be sure to subscribe for more like this :)

@shivamdashore6864 3 ай бұрын

@@tryexponent How can I use this type of whiteboard ? Is it free of I have to pay something to use ?

@udb_music 11 ай бұрын

After scrolling through 100s of SD videos finally I found a way to approach the questions in the interviews. Your step by step approach from start to finish was really helpful. Thanks

@kimnguyen1227 9 ай бұрын

I like the pace and structure of this video. What helps is that I worked on my design and looked at this video to see how well I did. One revision I would make is adding a object storage proxy and the backend service would call the proxy instead for protected images. To me, object storage is the toughest part of this problem. Public images can be served with cdn but private photos must retrieve from object storage.

@AmanVerma-lt7px 2 жыл бұрын

This is a great video and I haven't evenr watched it complete. I really like how the requirements are collected and quantified

@anandjain8668 3 жыл бұрын

I loved this video. You explained in such a easy way. i was able to connect everything. Thanks man :)

@nickcocks2745 3 жыл бұрын

Love this! Have my first ever systems design interview tomorrow and the broadness and pace of this interview is perfect!

@tryexponent 3 жыл бұрын

You got this!

@nickcocks2745 3 жыл бұрын

@@tryexponent An update! I'm onto the next round (onsite) in no small part thanks to this video!

@db13162 3 жыл бұрын

@@nickcocks2745 Keep on!

@RomainJouin 3 жыл бұрын

How did it go ? Is that the kind of answer that was expected by your interviewer ?

@nickcocks2745 3 жыл бұрын

@@RomainJouin I GOT THE JOB :) so it seems so! It's my first ever software engineering job (YAY!) so they were more looking for how I broke problems down and communicated than they were really grilling me on systems engineering, I managed to also squeeze in a mock interview before the real one and I used this video as reference material

@vennyroxz 3 жыл бұрын

Loved the video, great explanation. What is the UI/ tool used here to draw for the system design?

@tryexponent 3 жыл бұрын

It’s called Whimsical!

@OffbeatTravelVK 2 жыл бұрын

Really helpful video Jacob, super detailed in explaining the architecture. Thank you

@shehbazjaffer 3 жыл бұрын

Excellent Video! I was wondering what rationale should an interviewee give if asked about the scalability (specifically, write scalability) after choosing a relational database model?

@rohitparthasarathy6671 3 жыл бұрын

Wow - You just earned an subscriber - Excellent pace and detail Thanks !!

@prashantsingh1096 3 жыл бұрын

Thank you . This video shows that even hard topic like system design can be taught in a simple way . I like this .

@tryexponent 3 жыл бұрын

Glad it was helpful!

@daveB133 2 жыл бұрын

Anyone have any thoughts around the choice to go with SLQ (as opposed to NoSQL)? I’m relatively new to system design, but Twitter sounds like it would benefit more from the scalability that NoSQL would provide?

@basselabuelhija7366 2 жыл бұрын

Thanks for the video! Really enjoyed it as it gives a great exploration of the problem. However, I think the candidate needs to further explore the scaling of the data and provide estimations about read/write requests per second, traffic and storage needed that we need for instance for 10 years, and what to do when the DB is full that we need to scale vertically (as we you have gone for a MySQL). Those information will help out understanding the overall scale of our system and brightens the scene for the interviewer that we are set with with expected traffic and can manage to handle the requests.

@LaVengeanceInc Жыл бұрын

The feed generation part needs a bit more detail IMO. That's the most challenging part of this. Would you generate it on read or on write? Or a combination of both? Also, what if it's not a linear timeline of events but needs to be ranked? Also, details around comments and replies?

@thatsamorais584 3 жыл бұрын

This was an enormous help in my interview today! I adapted the flow to talk about the specific requirements. Calculating scale and talking about the data model with a segue into the overview diagram was very coherent. Most of all it produced every possible opportunity to highlight my experience with the components I presented, which is the overall goal.

@tryexponent 3 жыл бұрын

I'm so glad this was helpful Alex! Definitely let us know how the interview went!

@thatsamorais584 3 жыл бұрын

@@tryexponent I moved forward in the process, and the SDI was a large part of it! I discovered through the interview process about their product and the responsibilities of the role that it was not what I would like to pursue, but that's a different story.

@tryexponent 3 жыл бұрын

@@thatsamorais584 Congratulations!!

@_johnathan 3 жыл бұрын

Really wish I had seen this before my second round TPM interview at a major FAANG company. LOL Great video!

@tryexponent 3 жыл бұрын

Glad you enjoyed it!

@markp9827 3 жыл бұрын

I think this video is really very generic, so much so that this design could be applied to any problem. Would have loved see you deep diving into details of any one component in this 30 min video. For e.g is database sharing required? Do we need noSQL databases? how would the fan out process work? How to handle influencers who have 5 million followers? Disappointed to see those details missing here.

@nextlevelgamestudios 3 жыл бұрын

I would think for say N-Million followers, that work is either broken down aycnch and its broken across a number of shards in a region.

@Damouse007 3 жыл бұрын

He spent the whole time on the easier part of the design. He didn't model the feed, or describe when and how its built.

@nextlevelgamestudios 3 жыл бұрын

@@Damouse007 I think recently I just saw a architecture mock interview for Twitter in which they go over is designing the seed which was actually genuinely helpful it’s a very interesting approach to modeling I would probably look that up if you’re interested

@namanmishra08 Жыл бұрын

Agreed, this much detail will not clear a system design interview

@yobbei 2 жыл бұрын

Great video. Have you considered talking more about the APIs?

@user-xd3qb9ok9i 3 жыл бұрын

Nice pace of the mock interview. However, the diagram can actually fit most of the system. Shouldn't we focus more on how to fan-out photos, generate news feed, etc, which are more specific to "designing Instagram"? I wonder if we only talk about the high-level things and teaching the interviewers those basic architectural concepts (read-write, load balancer, s3, CDN) as this video does can really ace the interview.

@denebgarza 3 жыл бұрын

I kept waiting for the actual system design to start. Then the video ended. What this video covered is basically the skeleton of any system where you upload/view single files at a time.

@BrijeshBolar79 3 жыл бұрын

Yes found it to be really basic. Even I was looking forward to fanning out photos as well some replication to the dB as only one dB instance is used for both read and write operations for 10 million users

@kyletham9914 3 жыл бұрын

@@BrijeshBolar79 what does fanning out photos mean in this context? and any good resource on db replication / sclaing? thought that part was lacking definitely.

@tsaregrad 3 жыл бұрын

I see that in so many videos on KZfaq. 0 specifics about the actual system, just generic LB, DB schema, object storage stuff. I really wonder if interviews are buying this….

@denebgarza 3 жыл бұрын

@@tsaregrad they're not. You won't get any reputable offer with details KZfaq videos provide. These are just for the views.

@ryanm6528 2 жыл бұрын

Very good video for very novice engineers looking to learn about systems. However, there are big gaps here when it comes to scaling, ie. using a relational database (which also decreases performance) and having a synchronous system.

@rodoherty1 2 жыл бұрын

I had some questions about this, too. I can see the rationale for an RDBMS but from a scaling perspective, it would surely run into trouble. I was hoping the video might discuss how failover to another Region. The topic of Failover would surely come up in an interview.

@appstuff5778 3 жыл бұрын

Do you have any videos that talk more in depth about mobile architecture? For example battery usage, disk space on the device, networking speeds and data consumption of the device etc. If not do you know of any resources that have that info? Currently studying for FB design interview as an iOS engineer

@hewhocanfly 2 жыл бұрын

Good explanation. You made a complicated problem easy to follow and understand!

@jamiepearcey9335 3 жыл бұрын

I am not sure that a relational database is the best choice here. There are often relationships in data but sometimes you need to determine the right trade offs in terms of scalability. Though I appreciate that a relational model can be designed to work at such scale (read replicas, sharing etc), I would consider using NoSQL solution for the media metadata api, and a graph database for the activity feed.

@jasper5016 2 жыл бұрын

I have a question @22.05, you mentioned that when we will write data, we will write cache as well. If there is consistent write operation happening, you will keep changing cache. Would not it be more inefficient?

@RohanShetty1992 3 жыл бұрын

Great work , I learnt a lot today and the video was well paced and informative. Thanks

@tryexponent 3 жыл бұрын

Glad it was helpful!

@user-hh8fe2jk6p 2 жыл бұрын

Hello! What are you use for draw structure in this video?

@lankan526 3 жыл бұрын

Nice video! Do you think you could go over potential bottlenecks and how you would resolve those?

@tannerbarcelos6880 3 жыл бұрын

Learned a ton from this. Never have had a Systems interview and I am a new grad so my potential onsite coming up has a design portion so trying to grind through these and learn a ton!

@tarunstv796 3 жыл бұрын

Ton?!

@arobot4398 3 жыл бұрын

doesn't make sense asking a fresh grad system design questions.

@SumedhSen97 2 жыл бұрын

I am a new grad as well and have a sys design interview coming up. How deep did you go in the system? what all did you discuss and what all did you leave abstracted?

@ernestmummey6446 2 жыл бұрын

@@arobot4398 I have a interview coming up that is a system design interview, they are pretty common to be honest

@ConernicusRex 2 жыл бұрын

@@arobot4398 most F500s who want to hire anything above entry level often have at least one systems design and architecture interview in the process.

@sugurulovestokyo1260 2 жыл бұрын

Thank you for posting this! Really helpful!

@deathbombs 3 жыл бұрын

how about using object store for images, combined with DB for personal data?

@truemanrt 3 жыл бұрын

Good video, it would help if you can include rest interfaces (not in great detail, but something) as well in the future. A bit more diving into depth would help.

@MrNate858 3 жыл бұрын

What program do you to make these designs on your videos?

@vlad7780 3 жыл бұрын

Great video, thank you. Good example of CQRS in action. For further improvement it would be a good idea to use another DB for feed generation, because access patterns will be slightly different: OLTP for user actions and OLAP for feed (maybe some recommendation system under the hood).

@richann6637 2 жыл бұрын

Nice video! Which software do you use for the diagram?

@BABEENGINEER Жыл бұрын

What if you're asked to build a Logging API? Then it would just be client-side right? Would you go into details about servers and databases if it's mostly client-side?

@mrarun8007 2 жыл бұрын

Great stuff. Please post some mock interviews where the candidates failed. Thank you.

@srki80 3 жыл бұрын

What is the tool you are using for drawing/diagraming?

@dmytroportianka3842 3 жыл бұрын

so as I understood there is one DB without shards or replication. The question that bothers me is how many simultaneous requests one DB can handle? and one more thing is how data would be freed from cache? and what size of cache are you expecting to have?

@kumarashutosh229 2 жыл бұрын

It's all about how not to answer your design question! I mean, really this is how you design an instagram, or in a more generic sense any feed system? Note: These are my personal opinion. I would rather say these are the points that I was expecting from a 5+ year experieced dev perspective. He never talked about "post" and related stuff. Is instagram all about uploading your profile pic? Everything you upload would be a post and you may add image/file/feeling/re-share etc. Where is your post table and id? Are you going to use integer for storing your user-ids? Think again! He also did not mention the space incurred from text data, 1 PB of space would just for images. I guess we can use geo-location based storage. Notification being one of the most important component in any social-media platform. It should have been covered in requirements. I was expecting him to cover the latency in uploading images and the wireframe for image upload and render. Last but not the least, the re-share functionality! How to deal to re-post/share a post. I'm not being a pessimist, just thought to put my points. Apologies. Nice work btw

@deathbombs 3 жыл бұрын

Should client be calling to web server before the app server? App server handles business logic, web server handles the user's requests

2 жыл бұрын

Really nice video! Thanks! What is this program you're using through the entire video?

@tonyhuang9959 3 жыл бұрын

very helpful, can you make a more mock system design interview!!!????? thanks!

@tryexponent 3 жыл бұрын

Sure thing!

@moinmaster3516 3 жыл бұрын

so good, which tool are your using for capturing this all designing detail on one screen

@Criiz22 3 жыл бұрын

Thanks so much for this video! I loved it!

@tryexponent 3 жыл бұрын

We're glad you loved it!

@user-sk7dj6lw9d 3 жыл бұрын

Actually I think a write-through cache, or cache-aside to the write service will be easier to generate the feed. Bcs the cache server will know what content is pushed recently.

@ConernicusRex 2 жыл бұрын

So will the objects themselves who are stored with time and location data. Any component dealing with those objects will have that data, not just the cache. You want the use case to be “new to the user” not “new to the system” anyway.

@andywu9774 2 жыл бұрын

Can someone let me know which whiteboarding tool is used in the video please? Seems very useful!

@aditya8404 3 жыл бұрын

Why was the choice RDBMS and not something like a GraphDatabase as it makes more sense for querying on larger scale

@tommysuriel 2 жыл бұрын

Don't you need to use a CDN for the s3 distribution of images?

@irynasherepot9882 3 жыл бұрын

Thank you! Is this right - for every request for the image, there are two requests fired - one for image path from either cache or DB, and one for the image itself from S3 after the first requests executes? Thanks.

@irynasherepot9882 3 жыл бұрын

@@BitBlastBroadcast Thank you!

@afraz-khan Жыл бұрын

Its simple and compact, loved it, thanks.

@sourabh258 Жыл бұрын

Its nice, thank you ! 1. CDN could have been added 2. Encoding of videos and photos

@NinjiaJoeLife 2 жыл бұрын

what is the difference between load balancer and cdn? I guess both of them are for loading faster, distributed?

@boombasach 10 ай бұрын

Should we not consider a async queue before uploading to S3?

@BeHappyAndNice 11 ай бұрын

Thanks for sharing this amazing knowledge. I could not understand whether the generated feeds are stored in the cache based on each user or not. Because I think, storing feeds based on each user, causes Cache faces lots of hits.

@xiangweichen 2 жыл бұрын

What’s the drawing tool you are using? Looks really nice! Share a link?

@VideosVix1 2 жыл бұрын

hello, what app are you using for these sketches and notes? thanks great content!

@akashjain2990 3 жыл бұрын

Great video! Thanks for creating this content! I thoroughly liked the half hour video. If one thing I could suggest, would be little bit more deep dive into the design - API, sharding, replication etc. Also in case of read, you are connecting the mobile device directly to Object Store, then why not in case of write as well? The device can directly write to object store, and just push meta data through the App server (write). Are there any downsides you were thinking?

@stanislausaprankou3495 3 жыл бұрын

I might be wrong, since I'm also not an expert in system design, but my reasoning would be as follows: We can introduce a CDN between S3 and clients, making serving static files much faster. But I'm not sure if we can speed up the upload process (from the client to S3) in a similar way. Also writing directly to the S3 bucket just doesn't seem right to me from the security perspective

@Arrygoo 2 жыл бұрын

@@stanislausaprankou3495 you can request for a signed url from the server, and use that to upload directly to S3. Passing all those large files through the server is going to add so much unnecessary cost.

@noelomondi4849 3 жыл бұрын

I have a system design interview coming up next week, what tool are you using for sketching?

@furkan2640 2 жыл бұрын

Which tool you used in the interview can you mention please

@shambhavishindems4255 3 жыл бұрын

Can we use graphs to record follow relation between users?

@PradeepSingh-vm1gl 3 жыл бұрын

Yes. Graphs. Graphs database is best to store all the user's information & relationships between them. The response time for getting the relationship as well information about the user is so very fast with the Graph database. Graph databases are best suited for this type of many-2-many relationships as compared to the traditional relational databases. I do not agree with this guy saving user's details in the relational database. But basically, you must need all diff kind of databases for diff-diff purpose in such a large scale application. The architecture he designed is a common architecture for a simple mobile app. Have a look how complex the architecture can be for Instagram/Facebook. github.com/codekarle/system-design/blob/master/system-design-prep-material/architecture-diagrams/Facebook%20System%20Design.png

@ivantrofymenko1308 3 жыл бұрын

I'm far from an expert, but I disagree with your reasoning for choosing a SQL (relational) database. All data that's worth representing is relational in some way. That doesn't mean that SQL dbs are always the way to go. The types of queries you described can be performed efficiently on NoSQL dbs with smart use of indexes and would offer better scalability for a social platform like Instagram. No mention of Graph representation either, which is ideal for representing many to many relationships.

@tryexponent 4 жыл бұрын

Any questions about how to ace a system design interview question like this one? Ask below and we'll answer! Let us know what you liked!

@guitarist_covers 3 жыл бұрын

Couldn't we use a NoSQL data schema storing all the photos for a user along with the user object?

@uzoa.3504 2 жыл бұрын

Nice. What platform do you use for your presentation (video + slides) - Canva?

@sweetvoilet 2 жыл бұрын

Does anyone what is the diagramming tool used in this video? Thanks

@selvalooks 3 жыл бұрын

Good coverage !!! nice walk through !!!

@tryexponent 3 жыл бұрын

Glad you enjoyed it!

@meow-mi333 2 жыл бұрын

SQL for dynamic complex queries, ACID properties (some NoSQL also supports this). Relation or not is really not a strong reason. You can do the same in NoSQL with different tables using seperate requests or the same table using one request (Adjacency List Pattern). NoSQL for easy read/write scalability, high availability.

@devkashyap9049 Жыл бұрын

I came here to post the same comment and found your comment. Totally agree. It does not make sense to use SQL DB in this use case.

@edoardofoco216 2 жыл бұрын

What tool are you using to sketch out the architecture?

@SzymonKlepacz 3 жыл бұрын

How would you deal with comments and like to retrieve them quickly?

@amanpathania 2 жыл бұрын

What tool are you using to write the requirements?

@FizWiz91 3 жыл бұрын

Nice one. The connection between the metadata DB and the Cache got me wondering if it's possible to have a database trigger that actually updates a cache when data changes

@ManishKumar-mo6gx 3 жыл бұрын

Actually there will be a cache miss and then cache will go to the DB to get the updated data.

@user-ms9of1qn4w 3 жыл бұрын

This is great. The feed if generated in an hour it seems slow. Could you do it when a followed person updated 500ms ago?

@NianLi 2 жыл бұрын

500ms is too short. There are too many mappings, you even cannot finish the update within 500ms. (i.e. if the update has not finished, how can you start a new update). For huge data cache syncing, usually we would do database sharding and have multiple threads to update each category separately. This will boost the total speed. As for the updating time, it really depends, it could range from 1min - 1 hour and even 1 day (like billing information). But 500ms is totally unnecessary. As a user, can you feel any difference between 500ms and 10s? No. But it is a huge diff in CPU & RAM perspective, 10s = 500ms * 20 times!

@chandrashekar-ox7dr 2 жыл бұрын

can you tell which tool you are using for designing in this video

@kamalbalasubramanian621 2 жыл бұрын

what software is that you are using for the DFD?

@tttafooo 3 жыл бұрын

In a real interview If such a question is asked and one the requirements of the system is following someone than you definitely talk about CELEBRITY problem which interviewer is looking for in most interviews. It's most challenging and important part of such a system.

@sudhaganesh6419 3 жыл бұрын

Great presentation. Thank you :)

@tryexponent 3 жыл бұрын

Glad it was helpful!

@gqhl1003 3 жыл бұрын

Hi, thank you for proving this video, it is really helpful! Just to be clear, at 22:41, in the diagram, the cache policy you drawn seems to be a write-around cache policy, but at 21:56, you mentioned write-back cache policy (which I believe write operation is written to Cache first, and then after certain intervals, the data is written to DB). Did I understand this correctly?

@babajidedonald6899 2 жыл бұрын

Great! I have been looking for a more detailed system design interview. I'm glad I found this very explanatory and informative.

@RomilShah 3 жыл бұрын

Do we need to explain data modeling also? Seen first time in system design. In what cases I should be presenting database modelling and what cases I shouldn't?

@TheSlateOnline 3 жыл бұрын

You almost always have to do some data modeling, which isn't too difficult. I would assume you need to do it unless the interviewer interrupts you and says you don't need to. Usually, in system design, you are supposed to be driving the interview once you clarified the features.

@taheerahmed1120 2 жыл бұрын

Exponent provides best mock interview videos

@deathbombs 3 жыл бұрын

13:13 no table for relationship? That uses foreign keys?

@mysterio7385 2 жыл бұрын

The database model wouldn't scale, since we can potentially have n^2 rows in the follower table, where n is the number of users.

@kapil8965 4 жыл бұрын

Hey great video Jacob learned a lot. Really liked the way you explored everything giving fairly reasonable and convincing solutions . Thanks for the video again really appreciate the effort.

@tryexponent 4 жыл бұрын

Thanks Kapil! If we had to make another video next, what should the topic be? :)

@kapil8965 4 жыл бұрын

@@tryexponent Typeahead Suggestion or Twitter Search would be interesting topics .

@eibrahim 2 жыл бұрын

Very nice video. What is the tool you used in the video? Looks pretty slick and easy to use.

@petrob123 7 ай бұрын

Such a great explanation. Thank you.

@vishal.shetty 2 жыл бұрын

Thank you for this video, this is awesome. BTW which app you are using for designing the system?

@fatcat22able Жыл бұрын

It’s called Whimsical

@mariachowdhury1 2 жыл бұрын

Could you let me know the White Board Software that is being used for the interview?

@AnhNguyen-vu7mc 6 ай бұрын

a deep dive into the feed service would be greate. because obviously thats instagram's core feature

@kp-ws7do 3 жыл бұрын

Could you make a video about how to upload image and another video about how to design Instagram feed?

@saaaaaamy 3 жыл бұрын

So it's it a monolithic architecture? Or a micro services one?

@akshaysahu8880 2 жыл бұрын

which tool is being used to write the stuff in this interview?

@riteshthombre2846 3 жыл бұрын

Once the endpoint URLfor the image is figured out by making the search in MetaData DB, would a new request fire of again through the client to get that image through S3 or CDN? Or would thius happen in same request, as in we have an additional MicroService which would make a call to S3 or CDN and give back the image in same req?

@tryexponent 3 жыл бұрын

Hey @Ritesh Thombre! Typically the client will receive the first response from the web server, then make separate requests to the CDN for the image/video assets. This allows the client to optimize when to load these images for the best performance (e.g. when scrolling)

@riteshthombre2846 3 жыл бұрын

@@tryexponent Agreed. I guess, just a thing about design choice. Ours is a mini banking application and we make search of a customer's eStatement through its Metadata, get the DocID and generate the URL. Then hit the cloud storage and give back the document in same request. What you are proposing looks like will add another network call but that's fine. I think its a matter of design choice.

@drdr3496 3 жыл бұрын

19:19, jumped from talking about the application layer abruptly back to a physical implementation question (replication). That was weird and broke the flow of the scenario.

@abhi77kumar 2 жыл бұрын

Is it good to cache feed as this changes frequently.

@andrej7838 3 жыл бұрын

Hi, great video, one thing to take into account is that Instagram uses Cassandra as their primary DB, because of the partitioning, scaling issues relational databases have. While SQL databases are scaled vertically, NoSQL databases are scaled horizontally (scale-out across commodity servers). Also, NoSQL databases can store relationship data, they just store it differently than relational databases. So by saying that I wouldn't agree that a SQL database is the best choice here, at scale NoSQL is much faster, cheaper than a relational database

@mannydsz 3 жыл бұрын

You can scale sql databases horizontally using sharding and a decent shard key. Cassandra does that automatically for you if you categorize well your column families. If you mess you data model, you will have a bunch of hotspots on your cluster and will face the same problems of vertical scaling. The technology alone won’t solve your problem if you don’t know how to use it well. By the way, before Facebook bought Instagram it already scaled horizontally and used Postgres, which is a SQL database.