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Each example below is a complete design you can import: save the JSON as a file, open Streams → Create Stream, click Upload in the wizard header, and pick the file. The canvas and configuration load ready to explore — or to submit. To actually run one:
  1. Create its input topic on the Topics page (the topic names are in each example).
  2. Check Stream Properties — bootstrap.servers should point at your cluster.
  3. Submit, then produce a few messages to the input topic (Topics → Create Message) and watch the output topic.

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1 — Filter and transform (stateless)

demo-input → Filter → Map Values → demo-output. Keeps only records whose value contains error, then upper-cases them. Two SpEL expressions, no state — the smallest useful pipeline:

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2 — Word count (stateful)

The classic. text-lines → FlatMap Values (tokenize) → Group By (the word becomes the key) → Count → To Stream → word-counts.
Count produces a KTable of running totals, so its value type is Long — note the sink’s value serde. To Stream converts the table’s changelog back into a stream for the sink. Produce a few text lines and watch per-word counts accumulate on word-counts.

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3 — Tumbling-window count (windowed)

windowing-input → Group By Key → Tumbling Window (5 seconds) → Count → To Stream → Select Key → window-out-tumbling. Counts records per key, per 5-second window — the same count pattern as word count, but the total resets with each window instead of running forever. Grouping is by the existing key, and the window node just carries its size (windowSizeMs: 5000). One expression:
After a windowed count the key is Kafka’s Windowed object, not the plain key, and a String key serde cannot write it — without the unwrap the sink node carries an error badge and the deploy is refused. Select Key turns it into k1@5000, the key plus the window’s start, so the sink’s String key serde applies (windowed keys). Produce several messages with the same key in quick succession, wait past the window, produce again — the output shows a count per window, keyed by the window start.

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Where to go from here

Duplicate a node, change an expression, re-validate — the building guide covers the canvas, and the SpEL reference covers everything you can write in an expression. And remember to Download your variants: designs live in the file, not the server.