/1 Why is the credit card called โ๐ญ๐ก๐ ๐ฆ๐จ๐ฌ๐ญ ๐ฉ๐ซ๐จ๐๐ข๐ญ๐๐๐ฅ๐ product in banksโ? How does VISA/Mastercard make money?
The diagram below shows the economics of the credit card payment flow.
1. The cardholder pays a merchant $100 to buy a product.
/2 2. The merchant benefits from the use of the credit card with higher sales volume and needs to compensate the issuer and the card network for providing the payment service. The acquiring bank sets a fee with the merchant, called the โ๐ฆ๐๐ซ๐๐ก๐๐ง๐ญ ๐๐ข๐ฌ๐๐จ๐ฎ๐ง๐ญ ๐๐๐.โ
/3 3 - 4. The acquiring bank keeps $0.25 as the ๐๐๐ช๐ฎ๐ข๐ซ๐ข๐ง๐ ๐ฆ๐๐ซ๐ค๐ฎ๐ฉ, and $1.75 is paid to the issuing bank as the ๐ข๐ง๐ญ๐๐ซ๐๐ก๐๐ง๐ ๐ ๐๐๐. The merchant discount fee should cover the interchange fee.
/4 The interchange fee is set by the card network because it is less efficient for each issuing bank to negotiate fees with each merchant.
/5 5. The card network sets up the ๐ง๐๐ญ๐ฐ๐จ๐ซ๐ค ๐๐ฌ๐ฌ๐๐ฌ๐ฌ๐ฆ๐๐ง๐ญ๐ฌ ๐๐ง๐ ๐๐๐๐ฌ with each bank, which pays the card network for its services every month. For example, VISA charges a 0.11% assessment, plus a $0.0195 usage fee, for every swipe.
/6 6. The cardholder pays the issuing bank for its services.
Why should the issuing bank be compensated?
๐นThe issuer pays the merchant even if the cardholder fails to pay the issuer.
๐นThe issuer pays the merchant before the cardholder pays the issuer.
/7 ๐นThe issuer has other operating costs, including managing customer accounts, providing statements, fraud detection, risk management, clearing & settlement, etc.
Over to you: Does the card network charge the same interchange fee for big merchants as for small merchants?
1. How do video live streamings work on YouTube, TikTok live, or Twitch? The technique is called live streaming.
Livestreaming differs from regular streaming because the video content is sent via the internet in real-time, usually with a latency of just a few seconds.
2. The diagram below explains what happens behind the scenes to make this possible.
Step 1: The raw video data is captured by a microphone and camera. The data is sent to the server side.
3. Step 2: The video data is compressed and encoded. For example, the compressing algorithm separates the background and other video elements. After compression, the video is encoded to standards such as H.264.
The size of the video data is much smaller after this step.
1. Twitter and Reddit support NFT (Non-Fungible Token) profile pictures. Do you know what the differences between NFT profile pictures and regular profile pictures are?
The diagram below shows how NFT and regular images differ.
2. ๐๐๐ ๐ฎ๐ฅ๐๐ซ ๐ฉ๐ซ๐จ๐๐ข๐ฅ๐ pic
๐นStep 1: The user uploads a profile picture, and this request goes to the user service
๐นStep 2: The picture is stored in an object store, like Amazon S3. A URL is generated to visit the file
๐นStep 3: The pictureโs metadata is stored in DB
๐นStep 1: To understand the process, we should know what smart contracts are. Smart contracts are programs deployed and stored on blockchains. They are self-executing when predetermined conditions are met. This is when an NFT is โminted.โ
2. ๐๐ง ๐๐๐ง๐ค๐ข๐ง๐ ๐ฌ๐ฒ๐ฌ๐ญ๐๐ฆ๐ฌ
๐นDeposit process: Bob goes to Bank of America (BoA) to open an account and deposit $100. A new account B1234 is created in the wallet system for Bob. The cash goes to the bankโs vault and Bobโs wallet now has $100.
3. If Bob wants to use the banking services of Citibank (Citi,) he needs to go through the same process all over again.
1. How do we build a simple ๐๐ก๐๐ญ ๐๐ฉ๐ฉ๐ฅ๐ข๐๐๐ญ๐ข๐จ๐ง using ๐๐๐๐ข๐ฌ?
The diagram below shows how we can leverage the pub-sub functionality of Redis to develop a chat application.
2. ๐นStage 1: Connection Initialization
Steps 1 and 2: Bob opens the chat application. A web socket is established between the client and the server.
3. Steps 3 and 4: The pub-sub server establishes several connections to Redis. One connection is used to update the Redis data models and publish messages to a topic. Other connections are used to subscribe and listen to updates for topics.
In a large-scale distributed system, data does not fit on a single server. They are โdistributedโ across many machines. This is called horizontal scaling.