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Batch & Streaming · Streaming Processing

Polling vs push

Easystream-29
pollingpushingestionwebhooks

Question

What is the difference between polling and push-based data ingestion?

Solution

Polling: the consumer periodically asks "anything new?" on a schedule (every minute scrape an API, SELECT where updated_at > ?).

Push: the source sends data when it changes (webhooks, CDC to Kafka, agent shipping logs).

Polling:  consumer --tick--> source --maybe data--> consumer
Push:     source --event--> bus/consumer immediately

Trade-offs

  • Polling: simple, easy firewalls; wasteful empty polls; higher latency bounded by interval
  • Push: fresher; needs durable delivery, retries, auth, and backpressure design

Hybrid

Many stacks push into Kafka, then consumers poll Kafka (push to log, pull from log).

Interview tip: Explain latency vs complexity, then note Kafka consumers still *poll* the log even in event-driven designs.

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