Polling And Streaming

it is like a classroom, sometimes students ask the teacher lots of questions
- other times they quiet down and listen attentively to the teacher's lecture

When to use

when we are designing a system, if clients wants a piece of data that gets updated or that changes very regularly
- the clients are gonna have to be able to monitor the data changes (e.g.: temperature outside, or messages from a chat) in real time as the data will change a lot
  - the servers are gonna have this changing data, and clients are gonna need to see all these changes
in such cases, Polling and Streaming comes into play to help reflect these regular updates of data

the act of fetching a resource or piece of data regularly at an interval to make sure your data is not too stale
- e.g.: fetch data at every x number of seconds
However, it has limitations
- for apps like chat apps, you would want to send and receive messages instantly
- reducing the interval seconds can mimic the instantenous experience but comes with a trade off of having a lot of load on the server

in networking, it usually refers to the act of continuously getting a feed of information from a server by keeping an open connection between the 2 machines or processes
- typically referred to as a socket, which is a file that lives on your computer, that your computer can write to and read from, to communicate with another computer in a long lived connection, without having to repeatedly send requests
in Streaming, client is actively listening for data, and not requesting for data from servers
- it is the server's job to send the data to the client whenever the server gets an update
- in other words, the server will proactively push data to clients
one thing to take note is that, Streaming is not necessary better than polling
- Polling would be better if you need data updated not too frequently
  - e.g.: a dashboard that monitors stock prices and gives you a snapshot of stock prices at any given point in time, but not to allow users to do live trading