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Reactive operators chain together to form a processing pipeline. Each operator returns a new publisher describing the next step.

Common ones: map, flatMap, filter, take, buffer.

map transforms each item synchronously (1-to-1). flatMap transforms each item into another publisher and flattens the results — use it for async work.

map for pure, synchronous transformations.

flatMap when each item triggers an async call returning a Mono or Flux.

flatMap interleaves results as inner publishers complete, so order is not guaranteed. Use concatMap to preserve order.

Backpressure is the mechanism by which a slow consumer tells a fast producer to slow down.

Subscribers request a number of items; the producer only emits up to that demand. This prevents memory overflow.

take requests only the first N items, then cancels the upstream.

buffer groups items into lists, useful for batching.

When a producer is faster than the consumer, strategies control overflow: buffer, drop, or latest.

limitRate caps how many items are requested upstream at a time, applying controlled backpressure.

Real pipelines chain several operators to filter, transform, and limit a stream.

Test your understanding of operators and backpressure.

You learned about operators and backpressure:

• map = sync transform; flatMap = async, unordered; concatMap = async, ordered
• Backpressure lets slow consumers control fast producers
• take, buffer, limitRate shape the stream