System design interview - How online payment works using QR code?
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- เผยแพร่เมื่อ 6 มิ.ย. 2024
- QR code is common while doing online payment transfer. Here, I have talked about
1) using QR code for payment transaction
2) system design diagram
3) sequence of flows
4) Scaling the system
Similar methods are used in system designs like cash.app, venmo, paypal and google pay.
The two sequence I have discussed are
Sequence 1
-------------------
Buyer and seller registers in the system
Buyer goes to store and purchases item. (Stored in Buyer trans table)
Seller has the transaction stored (Stored in Seller trans table)
Seller shows the QR code to the Buyer generated by POS device
Buyers scan the QR code through his phone’s app.
Buyer enters the amount and clicks OK.
Money transferred from Buyer to Seller and receipt generated.
Transaction completes.
Sequence 2 (Paytm method for street vendors)
-------------------------------------------------------------------------------
Buyer and seller registers in the system
Seller downloads the QR code and displays in front of his store.
Buyer goes to store and purchases item. (Stored in Buyer trans table)
Buyers scan the QR code displayed in store through his phone’s app.
Buyer enters the amount and clicks OK.
Money transferred from Buyer to Seller
SMS notification sent to Seller and Buyer for confirmation
Transaction completes.
This is an amazon interview question and paytm interview question.
#systemdesign.
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• System design : Why do...
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Who am I ? : / keerthikanth
Hi , Thank you for making this video . It was great ! Can you advise me which type of QR code
would work well for a street performer or vendor ? .. and which type of cell phone would be required ? ... Thanks again for making available to all of us . Very nicely done :)
paypal, square all support this feature. Any smart phone will work.
@@ReachGoals Thanks a million brother ! It is very kind of you to help people as you have done so well :) You are an outstanding planetary citizen . Thank
you .
Impressive
Thanks. I am glade you like this video.
This is great Keerthi. I will provide my comments at a later time. I am also interested in the payments without QR code such as Venmo payments or via chat message. Will check into this as well. Contactless payments grew exponentially during pandemic.
@Usha, Thanks for the feedback.
great job
Thanks for support and I am glad you like this.
Hi thank you for sharing, I like your videos, can you make a video about cash payment system (the buyer select cash option on a website, get a QR code, walks to a store, pays, the store scan the QR code, get a bill on email and the order is on its way), front end and back end.
Great suggestion!
thank you :)
You're welcome!
Nice explanation . I've few questions here since you are referring to micro services and distributed systems,
1. Could you please throw some more detailed information around
a. Do you think all these are transactions synchronous or asynchronous ? Which of them could be synchronous and which of them could be asynchronous
2. Do you see any requirement for batch processing here?
3. If yes is the answer for 2nd question, what kind of tool and technology suits this level scale?
3. Do you see any need to use distributed streaming platforms like Kafka here?
1. In the financial world, transaction are sync. If not, the system will show the stale data.
2. Fintech is full of batch processing. If you need to do behind the scene data transfer, batch process is the recommended options.
3. Java spring batches.
4. When you send the data from one point to other, kafka can be used. This prevents single point of failure.
Thanks for this great video. My question is, is it possible for the seller to generate a unique QR code for each transaction, like say the code comes with amount for the item, and the buyer can accept or reject the amount?
Yes you can!
Thank you.
You'r welcome
What is Sega ? Is it any abbreviation ? Is saga implement into app or or not how it can interact with gateway ?
Nil,
The Saga is a design Pattern in microservices architectural to implement a transaction that spans multiple services. This is only of the way to have transaction in distributed databases.
SAGAS is a name of the publications and from there this pattern became popular.
This is the original publications as I said, it is named as SAGAS. I don't know why the Author named like SAGAS.:)
Refer here for original publications.
www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf
Also, There is another video th-cam.com/video/k925c1WN2LA/w-d-xo.html in this channel about how distributed transaction works in microservices. Please watch that and will be helpful.
Let me know if you have questions.
Hi @reachgoals
Can you please explain uses cases for how to do payment using registered mobile no and adding banking details like we do on phonepe and Google pay?
How to usee phone number or email to transfer funds ?
1) User A, B create an account using the phone number, emails, address in the app.
2) A, B will enroll in that app to use phone for payments/cash transfer.
3) When user A want to transfer funds to B, he will put B's phone number as Target.
- App will pull the details (account info) of B based on the phone(B's) number.
- A initiates a transfer. Cash is transferred from A' account to B's account.
Note: There are multiple levels of validation, encryption etc. happens internally and behind the scene. Hope this helps.
Surely it’s a great video 👍 but May you please answer one question that I have👇
Can we use QR code other way round as well for payments? For example, if the buyer has the QR code (registered/linked with their bank account) on some paper and the seller has the QR Code Scanner.
Now if the buyer presents their QR code to seller for payment of goods and seller then scans it onto their QR code scanner, as a result seller receives a message on their device asking to enter PIN which buyer will have to enter to approve the transaction. This PIN will be linked by buyer’s bank with their QR code for security purposes. Will it be possible? Remember buyer only has the QR Code and no other physical device with them.
Thank you
Yes this is possible. QR code is nothing but set of information.
This is similar to credit card usage. You give the card to shop keeper, he scans and you enter the pin on his device to complete the transaction.
Reach Goals Thank you
Explantion is good .But y do we require here 6 tables for db .We can have a table like User which has all these columns and one more column 'user_type' .When seller makes a transaction then this has to be populated with seller else buyer .This can be applicable for other two tables as well which you have shared .
You have to understand the Microservices based architecture. In the MS based architecture, database and tables are separated as per the services and use cases. Hence, I decided to do that. Also, you have to think about scalability, sharding etc.
This is the best video I have seen on the transactional process.... Are you available for private development? If so contact info?
Glad you like this. Hope it helps you.
Please make a video on how third party payment system of payments work like OYO- customer, oyo, hotels etc
sure, will do. thanks for feedback
@@ReachGoals waiting.....
Hi, may I said transaction for `payment` must follow the ACID principles, so we must choose `sql` database in this scenario? Thanks.
True.
But one important thing you didn't mention that if seller schema is successfully updated and then if buyer schema fails to commit , it should also rollback the transaction in seller schema. And that flow is also missing
yes, I didn't cover that. Good you shared in the comment.
Hello
If I engage a 3rd party to create a QR code
May I ask after a QR code is generated. Can the 3rd party help to change the QR code details again and funds get paid into another designated account
I am not sure. Keep in mind, QR code is created based on the certain content. If the content changes, new QR code has to be created. It's how you design the system
Your content is quite good, Few points which i have noticed.
1. When we are reviewing specific component of the system (ie Paytm) i am least bother about how Load Balancer and Mysql works.
2. In system scaling i am not seeing any usage of the CDN as per the current definition.
CDN will be there in all the system design. I didn't have as use case to shorten the video.
Loadbalancer will also be there in most of the system design when you have multiple servers.
Generally we dont create Seller and Buyer table, The idea is to keep it generic, something like user with a user account. The transactions happen from one account to another.
Any design is not written in hard stone. The design is debatable.
The reason I choose is to help in data base sharding in future.
what if createSaga failed after writing in the sellerTransactions and before commiting to buyer ?
it's good if you watch this shot video about the distributed transactions in micro-service th-cam.com/video/k925c1WN2LA/w-d-xo.html
You don't talk about trade offs at any point. This is one of the important criteria people see in system design interviews.
Thanks for the best feedback. Will think about it in the future videos.
Can you make a system design as to how Visa or Mastercard works
Sure, I will try to explain in the future videos.
I'm confused where to start my learning within your channel. please name videos by chapterwise like 1, 1.1, 1.2, 1.3, 2.1, 2.2 .. etc .
I have a play list. please check that.
Would you please share poc with zxing
I am not sure what you are asking? can you help me to understand?
Hi I need some help about SAGA
What help you need? Please share you question. I am happy to help you
In this video th-cam.com/video/k925c1WN2LA/w-d-xo.html I have simplified explanation of distributed transaction using SAGA. I believe, you will understand.