Don't Mix Up Polling and Pooling

In system design, two similar-sounding terms often cause confusion: polling and pooling. They address completely different challenges — one deals with when to act, the other with how to manage resources.

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Polling — Checking for New Data

Polling is when a consumer repeatedly checks if new data is available. The consumer tracks what it last saw (e.g., a timestamp or ID), then asks the producer:

“Is there anything newer than what I already have?”

If new data is available, the consumer then pulls it.

• Polling vs. Pulling:

  • Polling = "Do you have anything new?"
  • Pulling = "Okay, now give me the new thing."

Push — The Opposite Approach

In a push model, the producer sends new data directly to consumers whenever it becomes available.

• Push is event‑driven rather than time‑driven, often implemented using consumer webhooks. As soon as new data is ready, the producer sends it to the consumer via an HTTP POST or PUT request

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Pooling — Reusing Expensive Resources

Pooling refers to maintaining and reusing a fixed set of resources instead of creating new ones on demand. It is widely used for threads, database connections, or any object that is expensive to create and initialize.

• Examples:

  • Thread pool: Reuse a fixed number of threads.
  • DB connection pool: Maintain live DB connections to avoid reconnecting.

Think of it as:

“Don’t create a new one — grab one from the pool.”

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Summary

Term	Purpose	Example
Polling	Repeatedly check for updates	Checking job status, polling a queue
Pulling	Retrieve data when needed	Fetching new messages or records
Pushing	Send data as soon as it's ready	Webhook or POST from server to client
Pooling	Reuse heavy resources	Thread pool, DB connection pool

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Happy coding! 💻