Update backend roadmap

src/data/roadmaps/backend/backend.md

@@ -18,7 +18,7 @@ question:
     A backend developer is responsible for the development of server-side components of a web application i.e. working with databases, handling requests, creating server-side APIs that can be consumed by frontend developers to retrieve and manipulate data, ensuring the scalability of the systems i.e. making sure that the backend can handle a high volume of traffic and is performant, integrating external services like payment gateways, message queues, cloud services, etc.
 dimensions:
   width: 968
-  height: 2840.4
+  height: 2583.2
 schema:
   headline: 'Backend Developer Roadmap: What is Backend Development?'
   description: 'Learn what backend development is, what backend developers do and how to become one using our community-driven roadmap.'

src/data/roadmaps/backend/content/120-real-time-data.md

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+# Real Time Data
+
+There are many ways to get real time data from the backend. Some of them are:
+
+- Websockets
+- Server Sent Events
+- Long Polling
+- Short Polling

src/data/roadmaps/backend/content/123-long-polling.md

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+# Long Polling
+
+Long polling is a technique where the client polls the server for new data. However, if the server does not have any data available for the client, instead of sending an empty response, the server holds the request and waits for some specified period of time for new data to be available. If new data becomes available during that time, the server immediately sends a response to the client, completing the open request. If no new data becomes available and the timeout period specified by the client expires, the server sends a response indicating that fact. The client will then immediately re-request data from the server, creating a new request-response cycle.

src/data/roadmaps/backend/content/124-short-polling.md

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+# Short Polling
+
+Short polling is a technique where the client repeatedly polls the server for new data. This is the most common approach to polling. It's simple to implement and understand, but it's not the most efficient way of doing things.