System Design: Payment Gateway

System design for a payment gateway service (WITH idempotent auth-capture workflow!) by a FAANG Senior Engineer that has reviewed over 100 design documents 📚

Other names for this common system design interview question:
- Payment Service
- Payment System
- Distributed Ledger
- Digital Wallet

Examples of real world implementations of this:
- Stripe
- Paypal

Request other problems for me to cover here:

Here's a link to our discord channel where I organize the live discussions every weekend:

Originally recorded 11/26/2022

#systemdesign #programming #technology

[wy]

Auth and capture workflow wasn't really designed for idempotency, though you get it for free as you suggest (if payment processor generates the key). It was created for various use cases like:

- Gas stations, where you pay at the POS and need to authorize a certain amount before turning on the pump.
- Fraud use cases
- Insufficient funds use cases
- Hotels holding

Auth gives the merchant some level of guarantee prior to charging the customer that the payment tender is valid.

[featuresky]

I am just fascinated by some of the topics you covered including this one. Thank you. I haven’t watched it completely but I am going to for sure.

[maywilliams]

It would be good if you can condense these videos by cutting out a lot of extraneous chat. The videos are too long and can cause cognitive fatigue to continue following with extraneous things interspersed with slow design process.

[amaryadav]

I can't thank you enough for such a clear, constructive walkthrough and explanation! Btw I tried joining your Discord channel but couldn't. Thanks again for this entire channel with such an ocean of knowledge.

[maximizedchen]

should we use message queue instead of RPC calls if we use the orchestration?

[rahulramteke]

It would be nice if you could paste the 'Resource' section and its links in the description box/pinned comment

[AbdulRahim-bzoy]

Can I get your excalidraw board link for future reference.

[ErhanPatir]

Is "connecting to external system from internal" a correct design ? or do we need to add something while accessing external payment service for security ?

[niranjhankantharaj]

How do you handle the rate limit imposed by external payment service?
For eg, if the incoming request is at 100, 000 TPS (at peak time) and the external payment service only supports 10, 000TPS and rate limits other requests ?

[InfinteMotivation]

Explanation is good but the video quality is not appropriate. Screen is not clear.